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Lightnet: a Web based teaching tool

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Lightnet: a Web based teaching tool

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Content LIGHTNET: A WEB BASED TEACHING TOOL By Madhu Gupta A Thesis Presented to the FACULTY OF THE SCHOOL OF ARCHITECTURE UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment o f the Requirements for the Degree MASTER OF BUILDING SCIENCE (Building Science) August 1999 Copyright 1999 Madhu Gupta Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. U M I films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon th e quality of the copy subm itted. Broken or i ndistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send U M I a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6* x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact U M I directly to order. Bell & Howell Information and Learning 300 North Zeeb Road, Ann Arbor, M l 48106-1346 USA 800-521-0600 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS Copyrighted materials in this document have not been filmed at the request of the author. They are available for consultation at the author’s university library. figures on pages 3-9 This reproduction is the best copy available. UMI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number 1397652 __ ___ __® UMI UMI Microform 1397652 Copyright 2000 by Bell & Howel! Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. Bell & Howell Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UNIVERSITY OF SOUTHERN CALIFORNIA SCHOOL OF ARCHITECTURE UNIVERSITY PARK LOS ANGELES, CA 90089-0291 This thesis, written 6y toAPHU (rM jo rA _______________________ under the direction o f h&V_____Thesis Committee, and approved G y a d its members, has 6een presented to and accepted G y the (Dean o f The SchooC o f Architecture in partiaCfufidment o f the requirements fo r the degree o f <5£4J3A JgB - . < Dean ®afe_Li THESIS COMMI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Acknowledgements: I wish to thank........ My parents who have always provided me with unconditional support in whatever I ever did, I cannot thank them enough for their complete trust and confidence in my abilities. Professor Marc Schiler, Director o f the Building Science program, School of Architecture, University of Southern California who was the chairperson of my committee. I am grateful to him for a lot o f big and small things. Firstly for acceptance into this program and the financial support without which I would not have been here at all, his constant encouragement in whatever efforts I made and genuine pride in the results, for specially coming to school during vacation time to supervise my thesis, and last but not the least those lovely get-togethers in his cozy house. Professor Doug Noble and Karen Kensek, members of my committee who have been a constant source of ideas and suggestions alongwith some refreshing wit which helped lighten up some tense moments during my thesis. My roommate Jitender for being more than a roommate, the most reliable friend and family I had in school. In any endeavor there is one constant companion who is always there specially when needed most. He is the alter ego- always there guiding, helping, facilitating, encouraging, cajoling and re-energizing. I was fortunate in having Rajesh Arcot as my friend, guide and philosopher. I could not have taken on this task without Rajesh's constant presence and I cannot adequately express my thanks to him. ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table of Contents Acknow ledgments ii List of Figures V Abstract vii Part I Background 1 1.1 Introduction 1 1.2 Previous Work 2 1.2.1 Sites giving information on Artificial Lighting 3 1.2.2 Web Based Interactive Teaching Tools on other topics 6 Part II Lighting Concepts 1 1 2.1 Introduction 1 1 2.1.1 What is Light? 1 1 2.1.2 The Eye’s Response 13 2.1.3 Color Rendering 15 2.1.4 Light Level 17 2.1.5 Reflectance 18 2.1.6 Glare 18 2.2 Lamp Types 19 2.2.1 Incandescent 19 2.2.2 Fluorescent 21 2.2.3 Metal Halide 26 2.2.4 High Pressure Sodium 29 2.2.5 Low Pressure Sodium 32 2.2.6 Mercury Vapour 34 2.2.7 Light-Emitting Diodes 36 2.2.8 Electrodeless 38 2.3 Lighting Fixtures 40 2.3.1 Uplights 40 2.3.2 Downlights 43 2.3.3 Task lights 45 2.3.4 Tracklights 47 2.3.5 Spotlights 50 2.3.6 Linear Lighting 52 2.3.7 Cold Cathode Lighting 53 2.3.8 Emergency Lighting 54 2.4 Lighting Controls 55 2.4.1 Switches 55 2.4.2 Dimmers 56 2.4.3 Timers 57 2.4.4 Photocells 57 2.5 Comparisons 58 2.6 Calculations 59 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.6.1 Luminous Flux 59 2.6.2 Luminous Intensity 58 2.6.3 Illuminance 59 2.6.4 Exitance 60 2.6.5 Luminance 60 Part III Considerations for the Web medium 62 3.1 Planning 62 3.2 Organization of the Website 63 3.2.1 Chunking information 64 3.2.2 Relationships 66 3.2.3 Function 66 3.3 Designing Navigation System 68 3.3.1 Building Context 69 3.3.2 Improving Flexibility 73 3.3.3 Types of Navigation Systems 74 Part IV Lightnet; The Web Based Teaching Tool 82 4.1 Resources used and needed 82 4.2 Minimum hardware 82 4.3 Software 82 4.4 Structure and organization of Lightnet 83 Part V Conclusion 96 Bibliography 98 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. List or Figures Figure 1-1: Screenshot of Design-with-Lighting Site 3 Figure 1-2: Screenshot of Lighting Transformations site 4 Figure 1-3: Screenshot of Living Room design in LRC site 5 Figure 1-4: Screenshot of the Philips Lighting site 6 Figure 1-5: Screenshot of Interactive frog dissection tutorial 8 Figure 1-6: Screenshot of interactive tutorial on HTML 9 Figure 2-1: Electromagnetic spectrum 12 Figure 2-2: Spectral composition of natural daylight 12 Figure 2-3: Lytespread indirect lighting from Lightolier 43 Figure 2-4: Antenna uplighter 43 Figure 2-5: Semi recessed RZB 45 Figure 2-6: Recessed downlight 45 Figure 2-7: Hitech's cone-tasklight 47 Figure 2-8: Tracklight 49 Figure 2-9: Tracksystem 49 Figure 2-10: Spotlights from Microlights 51 Figure 2-11: Concord control spot 51 Figure 2-12: Linear light from Lightolier 53 Figure 2-13: Emergency lighting 55 Figure 3-1: Confusing site layout 66 Figure 3-2: Shallow site layout 67 Figure 3-3: Deep site layout 67 Figure 3-4: Balanced site layout 68 Figure 3-5: Screenshot of the Argus Clearinghouse site 70 Figure 3-6: Screenshot of the Infoseek site 71 Figure 3-7: Screenshot of lightnet showing navigation path 72 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 3-8: Screenshot from Lightnet showing navigation hierarchy 75 Figure 3-9: Screenshot of Controls page in Lightnet 76 Figure 3-10: Screenshot from Dimmers page of Lightnet 78 Figure 3-11: Screenshot of ProQuest Site 80 Figure 3-12: Screenshot of Lightnet showing embedded links 81 Figure 4-1: Opening shot from Lightnet 85 Figure 4-2: Screenshot of Index page from Lightnet 86 Figure 4-3: Screenshot of Information Center from Lightnet 86 Figure 4-4: Screenshot of First Page of Tutorial from Lightnet 87 Figure 4-5: Screenshot of Fundamentals Section from Lightnet 87 Figure 4-6: Screenshot of Introduction Section in Lightnet 88 Figure 4-7: Screenshot of lamps Section in Lightnet 88 Figure 4-8: Screenshot of Fixtures Section in Lightnet 89 Figure 4-9: Screenshot of Comparisons Section in Lightnet 89 Figure 4-10: Screenshot of Controls Section in Lightnet 90 Figure 4-11: Screenshot of Advisor Section from Lightnet 91 Figure 4-12: Screenshot of Calculator scetion from Lightnet 92 Figure 4-13: Screenshot of Help/Glossary section from Lightnet 93 Figure 4-14: Screenshot of Links section from Lightnet 94 Figure 4-15: Screenshot of Sitemap from Lightnet 95 Figure 4-16: Screenshot of Comments page from Lightnet 95 vi Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Abstract The purpose of this project is to create a Web Based educational teaching tool for Artificial Lighting. This project utilizes the crossplatform web-technology to illustrate the theory and applications of Artficial Lighting and Design. The aim is to demonstrate the effectiveness of an interactive tool over a textbook in educating lighting concepts. It also has a calculating tool to carry out some basic lighting calculations. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Part I: Background 1.1 Introduction Events of this decade have challenged many of the fundamentals of lighting design. The complexity of the art and science o f architectural illumination demands that understanding the psychological/ physiological/ environmental aspects of lighting be a primary consideration in future energy-conscious design. As architects and designers we have the unique opportunity to create environments for people and by doing so immeasurably enrich their lives. Lighting is an inseparable part of this responsibility, and it is the obligation of designers of buildings and places to realize and understand the significance o f light in all their creative endeavors. Unfortunately lighting remains a neglected topic for students, architects and designers who have not had formal courses in illumination and do not have the time to digest lengthy written descriptions. It remains a mysterious art form1 for numerous designers because of the apparent technical complexities. This is largely due to the fact that a lot of literature on the subject tends to be technical with lots of statistical charts, technical codes, standards, etc. These issues are important. However, it can throw off a beginner (read as students o f architecture, interior design, a layman interested in improving his surrounds through lighting) in the subject who does not have a compelling reason to learn the subject but would like to get an overview of the aspects and salient features of lighting. 1 Gardner, Cary and Hannaford, Barry, Lighting Design, John Wiley and Sons, Inc, p I 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A readily available, cross platform application that cruises through the fundamentals of the subject with interactive, fun to use graphics could help initiate a beginner. As with any other subject the web already has considerable material available, and a search on the topic throws up numerous sites. But none of them fulfil the requirements o f a teaching material for a beginner. They are usually one of the following: 1. Most commonly manufacturer’s websites which do have some interesting lighting facts albeit most of the content tends to point to their product as the most suitable for the considered examples. They also tend to contain a lot o f confusing, unrequired data. 2. Websites of organizations which, have useful information but may not be very comprehensible to the uninitiated. 3. Websites of Lighting Design firms. 4. Websites of Lighting Departments at schools. Etc. But unlike some other subjects where the interactive multimedia has been utilized extensively to teach and elucidate the concepts, not much is available on this topic. This is the gap that this tool intends to fulfil. 1.2 Previous Work This section deals with similar work done, and refers to two areas: 1. Teaching material available on the subject chosen i.e. Artificial Lighting on the net, but which the author found not to fulfil the requirements o f a basic teaching tool. 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2. Interactive Tutorials present on the net on other subjects (most commonly medical/biological sciences and computer science related subjects). A study was made of some o f the easy to learn tutorials available on other topics which inspired the treatment o f several interactive sections o f this tutorial. 1.2.1 Sites giving information on Artificial Lighting: 1. http://www.design-with-lighting.com/ This is a site of a company selling lighting fixtures and has an overview of the various light fixtures, and their uses. It is a little more than a manufacturer’s site as it goes on to describe each fixture type, and some advice on the lighting design of spaces. It serves as a good reference guide for a small section of lighting i.e. fixtures. Figure 1-1: Screenshot o f Design-with-Lighting Site Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2. http://www.ire.rpi.edu/Ltgtrans/ The Lighting Research Center (RPI) site has a section called Lighting Transformations, which has some sections which give basics of Lighting Design. The goals of this website is: 1. To conduct projects that speed the creation, entry, and penetration of new, energy- efficient lighting products into the commercial and residential markets, nationally and world-wide. 2. To establish the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute as an objective international resource for various organizations' lighting market transformation activities. To accomplish this goal the LRC offers technical information and advice, and assists in networking, planning, and facilitating activities for sponsors and their customers. Thus it has more of an advanced research content which is very useful, but intended for professionals with Figure 1-2: Screenshot o f Lighting Transformations site prior knowledge o f the subject. However it has some sections which deal with teaching some basic design facts and could be a starting point for learning, however this section has not been 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. developed and presently only covers residential lighting and describes living rooms. There is some linear interactivity. This kind of approach has been taken on in Lightnet however making the interactive images more interesting. The image below shows the screen shot of the page on lighting in living rooms, which has the image of a living n*»< m and clicking on a fixture brings up another page with information on that fixture. Figure 1-3: Screenshot o f Living Room design in LRC site 3. http://www.lighting.philiDs.coni/nam/howtolight/index.shtml The Philips site has a section on How to Light, which gives useful lighting tips in layman's terms with lots of graphics. However being a part of the Philips site this guide emphasizes on a Philips fixture as being the most suitable for every lighting need thus narrowing down the range. The “How to Light” Section in the Philips site is interesting, easy to use, covers a wide range of lighting problems and has lots of graphics but is has a limited perspective as far as fixtures are concerned. 5 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1-4: Screenshot of the Philips Lighting site 1.2.2 Web Based Interactive Teaching Took on other topics: 1 .http://www.explorescience.com/2 This site claims to be the first shocked3 science lab on the WWW (growing since December 1995). This site lets both students and teachers interact with material on the web, rather than just reading text. 2 Created by Raman PfafF, University of Michigan, Ann Arbor 3 Comes from the word Shockwave which is A technology developed by Macromedia, Inc. that enables webpages to include multimedia objects. To create a shockwave object, the Macromedia's multimedia authoring tool called Director is used, and then compressed with a program called Afterburner.. To see a Shockwave object, the Shockwave plug-in is needed, a program that integrates seamlessly with the web- browser. The plug-in is freely available firom Macromedia's Web site at www.macromedia.com. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. This site clearly accomplishes what it claims in a very effective manner. It covers the following topics: Mechanics, E+M, Life Sciences, Waves, Astro and Optics. Some o f the features which make this an ideal web based interactive teaching tool: • A short description of the topic being taught. Web users shy away from reading through loads of verbage and would skip through. • The cleverly designed interactive animations form the core of the teaching material, which allow users to move sliders or actual points/ planes to see the effect on the other variables graphically as well numerically. This approach does two things. Firstly it creates interest in the user because of the interesting graphics and also makes understanding the concept easier. • Being a graphics heavy site the author gives the option of downloading a compressed version of the whole site to the hard disc o f the user (specially useful for users who are on low bandwith) from where it can be run on a browser without any frustrating delays. • Provides links to download plugins which are required to view this site. • Includes a questions section regarding the site as to how it has been created, problems that could arise on different platforms, etc. All in all this site works very effectively both as a teaching tool as well as a web based application. 2. http://currv.edschooi.virginia.edu/go/frog/4 4 This program was initially developed by Richard Strauss, Jean Foss, and Mable Kinzie. It was ported to HTML by Bill Looney, Jason Mitchell, and Mable Kinzie. 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. This is an Interactive frog Dissection designed for use in high school biology classrooms. The purpose o f this lab activity is to help leam the anatomy of a frog and give a better understanding of the anatomy of vertebrate animals in general, including humans. This program provides still and motion visuals of preserved frogs, in addition to text. This program has a somewhat different approach to teaching than the previous one. However it is quite effective for the material it is dealing with. The interactivity here is of a more linear nature and short descriptions of the various procedures are accompanied by short movies, thus there is not much interactivity. One very useful feature in this tutorial is the practice session, in which the , . . . . . , , . ■ Figure 1-5: Screenshot of Interactive frog user has to graphically carry out what he/ she le dissection tutorial For instance after the user has watched a movie on how to pin the frog he/ she has to click on all the right points on an image to be successful in that practice, thus the user gets the virtual practice of pinning the frog. 3. http://fcit.coedu.usf.edu/tables/ This tutorial to teaches html tables but does that quite effectively wherein the user types in html script from what he/ she learns and can test it right there in a test window. 8 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The strong point o f this tutorial is enabling the user to test the script results at the same page instead o f opening up another editor application. The tutorial divides the browser into two frames: the top one for text descripition and the bottom one to test what you leam. The author has tried to include the useful Figure 1*6: Screenshot of interactive tutorial on HTML features from the various examples on web. The web-based teaching tool on Artificial Lighting attempts to serve as a useful learning tool for architecture/ interior design students to plug the gap in their current education. This tool is not a technical guide, nor an in-depth step-by-step lighting design guide, but more like an overview/ a primer to the topic o f lighting to serve as starters for someone who is relatively new to the subject. It might be nice for an architect to perform a quick lighting estimating calculations, but there is no need for everyone who practices design to understand flux transfer and Fourier series in detail. 9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. However the tool has been so structured that it can be developed further to illustrate and explore deeper into the subject to become a “easy to use” 1 reference tool for professionals too. 1 "Easy to use” compared to a book as the hyperlinking in a webtool makes it possible to go to the desired information in one or two clicks of the mouse button (provided it has an efficient navigation system of course) as against the having to shuffle through several pages in a book. 10 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Part II: Lighting Concepts 2.1 Introduction 2.1.1 What Is Light? Light is a form of electromagnetic radiation and is a major medium through which we discover the world around us. The world is made visible when light either emanating from the sun or artificially created, falls on objects. Some o f this light energy is reflected back into the eye and is decoded by the brain, to discern the particular size, movement, distance, shape, color and form of the objects concerned. The nature o f the light falling on our surrounding environment - its brightness, the angle at which it falls, and so on - can have a profound effect on how we perceive it. For example, we know that a landscape lit by bright sunshine looks totally different from the same landscape lit by "gray' light from a dull, overcast sky. Not only does the world look different, everything else being equal, this changed perception can have a strong psychological effect on viewers, even causing shifts from a happy optimistic mood to one of sadness, melancholy or even depression. There is now a clinical term, SAD (‘seasonal affective disorder1 ) to describe the condition suffered by some people, particularly those living in north latitudes.1 During the shorter days of winter, when daylight is limited and sunlight is minimal or even non-existent, people can feel sluggish, depressed and physically run-down. Exposure to substitute artificial daylight for periods each day has been shown to have beneficial effects on SAD sufferers and is sometimes used as a clinical treatment. The exact mechanisms o f this psychological malaise are, as yet, not fully understood. The power of light to influence 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. perception, mood and even the outward behavior of people, is one o f the most important aspects of designing with light. Light, like other forms of electromagnetic radiation such as heat, radio signals and X-rays, is transmitted in waves, which have a characteristic and unique wavelength. Visible light is emitted from a very narrow range in the electromagnetic spectrum, between 380 and 760 nanometers (nm). At longer wavelengths, energy is transmitted in infrared (heat radiation) and radio waves; at shorter wavelengths, it is transmitted as ultra-violet 'light'. X-rays and gamma rays. Within the narrow band (380-760nm) of visible light, each color from violet, through blue, green, yellow, orange and red has its own wavelength. When all these wavelengths are present together they produce a balanced mixture which we experience as 'white' light. If we shine white light through a glass prism, each of the different colors within the mixture is refracted (bent) at slightly different angles due to the different wavelengths. The result is that the 'mixture' of colors is 'unscrambled': each o f the individual colors becomes visible in the form of a spectrum of colors. Example: rainbow. Although changing in quality, average midday sunlight is generally Figure 2-2: Spectral composition of natural perceived to contain all the colois in daylight 1 Gardner, Karl and Hannaford, Barry, Lighting Design, John Wiley and sons, p. 2 12 ' • 00 200 300 400 500 600 700 800 10 * - * - fO fi ■ X~esv% 1 0 '* 1 0 10* 10* 10* 10 1 0 1 0 - ' 1 0 * — Figure 2-1: Electromagnetic spectrum Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the spectrum. No commercially available artificial lighting source can completely mimic natural daylight, though several come very close. All light emitted by lamps falls within the spectrum range of violet to red, but different light sources concentrate their output in particular parts of the spectrum, in different combinations (i.e. they have different spectral compositions, as also most lamps emit radiation in one of several invisible ranges, depending on lamp type). A lamp's specific spectral composition gives its emitted light a characteristic color appearance, and also determines its color rendering capacity. In some cases this light may appear unnatural or even uncomfortable to the viewer precisely because no close corollary appears in nature. 2.1.2 The Eye’s Response An important consideration is the eye's own response to light of different wavelengths. The nerve endings inside the eye are not equally responsive to all colors: in well-lit conditions they work most efficiently within the green-yellow areas of the spectrum and least efficiently at the extreme ends of the spectrum (i.e. with blue-violet light on the one hand, and red at the other). In darker conditions, when eyes have become 'dark adapted' (a process that can take upto an hour) their maximum responsiveness shifts towards the blue-green end of the spectrum, which is why, at night, green traffic lights seem to be much brighter than red ones. This differential responsiveness is the main reason why low-pressure sodium lamps are the most efficient lighting sources available. All o f the light they emit lies roughly at the middle o f the visible spectrum, where the human eye is most responsive. At that wavelength eyes 'need' less light to make sense of the world, so light levels can be 13 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. kept lower while still maintaining visibility and safety. Although sunlight is often taken as the norm by which natural 'white' light is judged, it too can change its quality and composition, depending on the time of day, season and prevailing meteorological conditions. Objects absorb from the light that falls on them (incident light) all its colors except the ones they give back (reflect). The surfaces of objects have differential reflective characteristics. For instance, a 'yellow1 painted object will reflect back yellow light (comprising red and green) but will absorb the blue; a 'green' object, on the other hand will absorb all the wavelengths in white except green, which is reflected back from its surface. With pigments in commercial materials, this process of absorption/ reflection is not perfect. Conversely, if we shine a purely green light onto a 'red' object, it will appear black (i.e. without color). In this case the green light has been absorbed by the 'red' surface, but because there are no red wavelengths present in the incident light, there are none to reflect back to the viewer. So, a black surface is one that absorbs all the spectral colors; a white surface is one, which reflects all o f them back. Thus colors are not intrinsic quality of objects; rather, colors are solely contained within light rays. The color appearance of light is most often expressed in terms of its particular color temperature. This is an objective measurement rated in degrees Kelvin (K) To understand the concept, think of an iron bar that is being slowly heated. It starts off black, and in the initial stages of heating it radiates only visible infra-red rays (i.e. heat); it then 14 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. changes to dull red as it heats up; as it gets hotter it appears more and more orange, then yellow and at very high temperatures it is as is commonly said, 'white hot. Each of these different color appearances corresponds to the different temperature states of the bar (i.e. the bar's color and its temperature are intimately related). The color temperature of a light source rises with its thermal temperature; the higher the temperature, the more blue the light. This may seem a paradox, since the lowest color temperatures achieve the 'warmest' lighting effects. For example a candle bums at a 'cool' 2000 degrees F C , but it offers a warm, yellow, comforting light; a 'cool' fluorescent lamp emits light at around 4000-5000 degrees K, which we experience as very blue and cold. Natural daylight is often seen as a norm, the natural benchmark against which other lighting can be judged. But the color temperature (and hence the appearance) of daylight varies widely. Summer midday sunlight lies roughly in the middle of the range between candlelight and a clear blue northern sky, at around 5500 K. Incandescent lighting, which has a lower color temperature than natural light, at between 2500 and 3500 degrees K, always appears warmer and more yellow. 2.1.3 Color Rendering The International Commission on Illumination (CIE) has developed a color- rendering index (CRI) which, by averaging their spectral content, ranks different sources from 0-100; the higher the number, the truer the color rendition at its color temperature. It is important to remember that when it comes to comparing the color-rendering capabilities of different lamps, this can be done only at the same color temperature. So, fluorescent and incandescent lamps at, say, 3000 degrees K can be meaningfully 15 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. compared for color rendering, but an incandescent lamp of 3000 degrees K and a fluorescent o f 4000 degrees K cannot. Correlated color temperature classes and color rendering groups used in the CIE code:2 CORRELATED COLOR TEMPERATURE (CCT) CCT CLASS CCT<=3300K warm 3300<CCT<=5300K intermediate 5300<CCT Cold COLOR RENDER1 NG GROUPS CIE GENERAL COLOR RENDERING INDEX (Ra) TYPICAL APPLICATION 1A Ra>=90 Wherever accurate color matching is required, e.g. color printing inspection. IB 80<=Ra<90 Wherever accurate color judgements are necessary and/or good color rendering is required for reasons o f appearance, e.g. shops and other commercial premises. 2 60<=Ra<80 Wherever moderate color rendering is required. 3 40<=Ra<60 Wherever color rendering is of little significance but marked distortion o f color is unacceptable. 4 20<=Ra<40 Wherever color rendering is of no importance at all and marked distortion of color is acceptable. 2 Gardner, Karl and Hannaford, Barry, Lighting Design, John Wiley and sons, p. 6 16 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.1.4 Light Level Apart from color aspect and rendering, also important is the quantity o f light used and the way it is distributed. Light has a number of measurable properties, all of them interrelated. We see an object because light flows from a source, hits the object’ s surface and some of it is reflected back to the eye. It is convenient to think of the process in four stages: a. The actual source: The initial luminous intensity of a source is measured in candelas (cd). This was based historically on the intensity of the standard candle, hence the name. In lighting design this unit is important when dealing with point source calculations. b. The flow of light from it: The flow of light from the source, or luminous flux, is measured in lumens (lm). This refers to the quantity of light emitted from a source (known erroneously as 'light output'). This unit is important for area lighting calculations (e.g. when determining the number and size of lamps to achieve a particular illuminance level). c. Its arrival at the object: When light arrives at an object or surface, we talk about its illuminance (the quantity o f light actually falling on it). This is measured in lux (lumens per square meter). Illuminance is an important determinant of the lighting level in the room, but it refers only to the light which falls upon particular surfaces, such as walls or work surfaces; it does not give any indication of how bright the room will appear. That will depend on the reflective properties of the surfaces. d. Its return from the object: how we perceive the lit surface or object depends on how much light is reflected back off it. This observed brightness, an object's luminance, is measured in candelas per square meter (cd/m). As indicated, the reflectance properties of 17 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the surface play an important role here. Similar illuminations can result in widely differing luminance. 2.1.5 Reflectance Reflectance relates to how much light is reflected by an object: for diffuse surfaces reflectance is a major determinant o f luminance; for specular surfaces angle of incidence is important, too. Roughly speaking, for a matt surface. Reflectance = Luminance X PI / Illuminance 3 Although other factors, such as the angle of incidence, and surface texture can affect the calculation. A reflectance factor is expressed as a unitless figure between 1 and 100 (ie a percentage), or as a decimalized fraction (eg 0.8, 0.6). 2.1.6 Glare Glare occurs when the eye has to cope with a source o f light, which is much brighter than the average level of lighting surrounding it. Such excessive contrast causes the muscle of the eye to adjust continually between the two levels of brightness, a process we find both tiring and stressful. 'Direct' glare is caused by primary source of illumination- the lamps and luminaires making up an installation (for example, a bright lamp which has been located against a dark background). 'Indirect glare' is due to secondary sources, such as light reflected off surfaces, which are excessively bright. 'Veiling reflections' from the screens of visual display terminals are a common example. Indirect glare may depend upon elements in the interior generally considered outside the J Boyce, P.R., Human Factors in Lighting, Macmillan Publishing Co., Inc., p. 5 18 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. scope of the lighting designer - surface o f wall or ceiling finishes, desktop materials and so on. The direct glare zone should be avoided in designing office lighting. The luminance of luminaires should be restricted between 5 and 30 degrees. 2.2 Lamp Types 2.2.1 Incandescent Incandescent lamp applications range from standard household light bulbs to highly specialized railroad signaling lights. These heat-based lamps generally use a tungsten filament. They have a life of 750 to 5000 hours. For many applications, more energy-efficient compact fluorescents, full-size fluorescents, or high intensity discharge lighting should replace incandescents. "Energy-saving" incandescent lamps use less energy but also deliver less light, offering negligible efficiency benefits. Halogen lamps are incandescents that use a halogen gas to redeposit evaporated tungsten back on the filament. Halogen lamps in the standard residential incandescent shape are about 15% more efficient than regular incandescents. Halogen IR lamps retain some of the heat produced by the lamp by reflecting the infrared (IR) energy back to the filament, increasing their efficiency about 30-40% above regular halogen reflector lamps. The 1992 Federal Energy Policy Act established minimum efficiencies, banning most standard incandescent floodlights and spotlights after November 1, 1995. More efficient halogen, fluorescent, and HID sources will replace that part of the market. 19 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Aesthetics: Lighting Quality: Used as a reference standard for lighting, incandescents have a color rendering index of 100 by definition. Halogens produce a slightly whiter color (more towards blue) than standard incandescents. Size: A wide range of incandescents are available, from 4-1500 watts. Light Intensity : Lumen Output Range: 16-36,000+ lumens. Ability to Focus Light: Incandescents can be easily focused and directed, making them an excellent choice for specialized applications such as jewelry displays, as well as for general lighting. Efficacy : Lumens/Watt: Incandescents can produce up to 36 lumens/watt, although most lamps produce 15-20 lumens/watt. Temperature Impacts: None. Applications: Incandescents have a wide variety o f applications, from household use to spotlights to directed display lighting. Although inefficient, these compact lamps are optimal in Iow-use areas, or locations requiring dimming. Their superior ability to focus and aim light well makes them well-suited for spotlighting. Controls • Ballasts: Incandescents do not use ballasts. • Timers: Because of their instant operation, incandescents are a good lamp to use with timers. • Occupancy Sensors: Incandescents provide a ready light source when used with sensors. • Dimming: Incandescents can be dimmed very easily and inexpensively. On/OfT Characteristics: Incandescents are capable of instant on/off operation. 20 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Lighting/HVAC Interactions. Savings Beyond Lamp/Ballast Reduction: In areas that use air conditioning, upgrading from incandescents to more-efficient halogens can provide only a slight air conditioning savings, in addition to lighting energy savings. Maintenance: • Lamp Lumen Depreciation: A standard incandescent produces about 15% less light by the end of its life, whereas a halogen loses only 5% of its light output by the end of its life. • Cleaning Impacts: Planned cleaning and group relamping typically results in a 15% energy savings, because fewer fixtures can be used. 2.2.2 Fluorescent Efficient and versatile, fluorescent lamps are the most widely used type of lighting in commercial facilities. Better ballasts have done away with flicker and buzz, while rare-earth phosphors have improved color rendering and efficacy. Full-size or compact, fluorescent lamps are available in a variety of shapes and sizes, ranging from little 5 watt T-4 twin tubes to powerful 215-watt VHO lamps. Aesthetics Lighting Quality: A fluorescent's quality is directly related to its phosphor coating. Standard halophosphors— the traditional "cool white" lamps— produce light with a color rendering index (CRI) of 60-62. Premium halophosphors boost the CRI to over 90, but reduce lamp lumen output. Best performance is obtained from phosphors containing rare earth (RE) metals. RE-70 lamps yield a CRI of 70-79; the more expensive RE-80 lamps 21 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. produce a CRI of 80-89. What's more, RE phosphors increase lumen output-5-6% for RE-70s and up to 8% for RE-80s~as well as minimize lamp lumen depreciation. Full-size fluorescent lamps come in a wide range of color temperatures: 2700-7500K. Compact fluorescent lamps (CFL) are available in color temperatures ranging from 2700-5000K. and produce good quality light using RE-80 phosphors. Size: Lamp size and shape can be determined from the lamp model designation. For example, F40/T12/CW/HO/WM translates as follows: F = fluorescent 40 = wattage (except for energy-saver lamps and units longer than 48 inches, where the number equals the length of the bulb in inches) T = tubular shape 12 = diameter in eights of an inch (12/8 = 1.5 inches); other common sizes are T-5, T-8 and T-10 CW = cool white, indicating lighting color; other manufacturer-specific labels such as SP35 and D835 are also used to indicate phosphor type and color temperature HO = high output; VHO (very high output) is another option; included only if appropriate WM = Watt-Miser(R); manufacturer-specific designation for energy-saver lamp; other designations include SS (SuperSaver(R)) and EW (Econ-o-watt(R)); included only if appropriate. Full-size fluorescents (T-8 to T-12) range from 12 inches (13 watts) to 96 inches (215 watts). Other "full-size" units include two-foot long U-bent shapes (T-8 and T-12). Because the 1992 Federal Energy Policy Act prohibits sale of the old standby 2 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F40/T12/CW lamps after November I, 1995; lower wattage F40/T12/WM lamps or higher quality units with RE-70 or RE-80 phosphors are now used instead. CFLs in T-4 and T-5 sizes (5 to 34 watts) come in a wealth of shapes, including 2-leg (twin tube), 4-leg (quad tube), 6-leg (triple-twin tube), and 8-leg;two-dimensional squares; circular; and helical. Two-foot long single-twin-tubes (39 to 50 watts) offer an alternative to full-size T-12 or T-8 lamps for office-type lighting. Some are packaged as bare lamps while others are put in globes or include reflectors. Integral models include a disposable ballast and adapter that can screw directly into an incandescent socket. Light Intensity Lumen Output Range: Full-size fluorescents range from 565 lumens for a 13-watt T-8 to 15,700 lumens for a F96/T12/VHO. Common 4-foot lamps produce about 4000 lumens. CFLs range from 250 lumens for a 5-watt compact lamp to 4000 for 50-watt lamp. Most CFLs are position-sensitive; light output can drop 15-20% if the lamp is installed base down. Ability to Focus Light: Fluorescent lamps spread diffuse illumination along the tube rather than providing a focused point source, making them inappropriate for spotlighting. CFLs provide adequate lighting for general downlighting applications. Efficacy Lumens/Watt: Efficacy (lm/W) depends on: Phosphor (RE is best) Lamp length (the longer the better) Ballast type (electronic versions improve efficacy) 23 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Full-size lamps range from 55 to 90 lm/W. Efficacy is lower for HO (50-85 lm/W) and 1500 mA VHO (50-60 lm/W). CFLs range from 25 to 85 lm/W, generally delivering 50- 60. Temperature Impacts: All fluorescents have an optimum performance temperature and efficacy suffers below or above that point. Full-size fluorescents in recessed lensed fixtures, a common configuration, typically operate above the optimal temperature, resulting in efficacy loss. Extreme temperatures can reduce light output 20% or more for all CFLs, and CFLs less than 10 watts can resist starting in temperatures below 40 degrees F. An amalgam used in some CFLs greatly reduces the temperature and position performance penalties. Applications Popular Applications: Full-size fluorescents are used for most commercial interior lighting. These units typically light spaces where the use o f computer visual display terminals raises issues of screen glare and proper light levels. Fluorescents are less appropriate for ceilings over 15ft. where high-intensity discharge lighting is superior. The HO and VHO lamps are appropriate for areas with high ceilings or higher light-level requirements. CFLs can replace incandescents o f less than 150 watts in most applications: general lighting, downlighting, or decorative lighting such as pendants or wall sconces. Because the lamps are larger than most incandescents, make sure they fit the luminaire. CFLs are not recommended for ceilings higher than 15 ft., cold exterior locations, or most retail spotlighting. Retrofit: With an excellent selection of high-efficiency components available, many fluorescent luminaires can be retrofitted to reduce energy use. 24 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Controls • Ballasts: Virtually all fluorescent lamp sizes require a unique ballast. Selecting the proper ballast is key to optimum system performance. Premium ballasts are available for many common types such as CFLs, and 4-ft. T-12 and T-8 lamps. Energy-efficient electromagnetic ballasts are giving way to slightly more expensive electronic ballasts, which improve lamp and system efficacy, reduce flicker and hum, and weigh less. Cathode cutout ballasts are also available, offering performance nearly indentical to electronic ballasts. Older, inefficient electromagnetic ballasts were banned in the United States in 1990. • Timers: Fluorescents can be used with almost any timer. • Occupancy Sensors: Although they are appropriate for use with occupancy sensors, fluorescent lamp life depends on how often and how many times the lights are switched on and off. Instant-start type lamps have shorter life. Frequent on/off switching will reduce lamp life, although the life penalty is minimal for most commercial applications. • Dimming: An increasing number of dimming ballasts are available. Most are electronic. • On/Off Characteristics: Starting time o f electronically ballasted lamps is typically less than one second, while magnetically ballasted lamps typically require 1 -4 seconds to start. Fluorescent longevity is affected by the number of times the lamp is switched on and off during its life; manufacturer's life ratings are based on 3 hours of operation per start. Lighting/HVAC Interactions Savings Beyond Lamp/Ballast Reduction: Because fluorescents are typically used in commercial facilities with air conditioning, upgrading from a less-efficient source like 25 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. incandescent or inefficient fluorescents provides air conditioning savings in addition to lighting energy savings. Maintenance Lamp Lumen Depreciation: Cool white or warm white fluorescent lamps maintain about 80% of their initial lumen rating through the end o f their life-better than metal halide, mercury vapor, or high pressure sodium lamps. Triphosphor (RE-70 or RE-80) lamps are even better, maintaining about 90% of initial lumens. HO or VHO models depreciate considerably faster: Three-quarters through their rated life, HO lamps produce 24% less light, while 1500 mA VHO lamps produce 35% less. Cleaning Impacts: Planned cleaning and group reiamping typically results in a 15% energy savings, because fewer fixtures can be used. 2.2.3 Metal Halide Metal halide lamps are among the preferred high-intensity discharge (HID) lamps. Used in situations where high-quality lighting is necessary, applications range from office building downlighting to sports stadium lighting. They are can produce more lumens than larger fluorescent sources. Compared to incandescent or mercury vapor lamps, metal halides offer substantial energy savings, generating less heat, and reducing air conditioning loads. They are two to five times more efficient than incandescents. Full- size and compact lamps are available in a variety o f designs, with life spans ranging from 2,000 to 20,000 hours. Aesthetics: Lighting Quality: Lamp colors can match incandescent, fluorescent, or daylight, with a medium to high color rendering index (50-100). 26 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Size: Full-size metal halides range from 175-1500 watts; compact lamps, from 32-1500 watts. Light Intensity Lumen Output Range: 2,500-110,000 lumens. Ability to Focus Light: Because metal halides produce a bright near-point source, their output can be directed and controlled well for use in downlighting and track lighting. This is particularly true for compact metal halides. Efficacy Lumens/Watt: Full-size, 55-100 lumens/watt; compact, 50-90 lumens/watt. Temperature Impacts: Metal halide lamps are sensitive to low starting temperatures, and lamp life will be reduced if they are frequently started below -12 degrees C (10 degrees F). Applications Popular Applications: Most appropriate for areas requiring many hours of uninterrupted lighting that have ceilings higher than 15 feet. Large, high-output luminaires are used in high- or low-bay commercial and industrial lighting, downlights, street lighting, and sports field lighting. Compact metal halides are used in downlights, wall washers, exterior lanterns, and globes. Double-ended lamps are primarily used in designs similar to those for double-ended tungsten-halogen lamps. Metal halides are a good retrofit for systems using incandescents of 150 watts or greater. 2 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Controls • Ballasts: Ballasts are required to operate metal halide lamps. Electronic ballasts for metal halides manage the lamp's arc tube wattage precisely, maintaining color consistency and increasing lamp life. • Timers: Appropriate for applications not needing instant operation. Tungsten-halogen option available for some luminaires requiring instant operation. • Occupancy Sensors: Standard metal halides are not appropriate for occupancy-sensing because they provide inadequate light during warm-up. However, high/low ballasts can provide full lighting during occupied periods and reduced light during unoccupied periods. • Dimming: Requires specialized ballasts and dimming electronics. Metal halide lamps operating at less than full output will produce color shift and reduce lamp efficacy. High/low ballasts can provide an alternate solution. • On/Off Characteristics: Warm-up can take from 2 to 10 minutes. If the lamp's arc is interrupted while lit, most lamps must cool before the arc can restrike. However, instant restrike lamps are available for some sizes. Lighting/HVAC Interactions Savings Beyond Lamp/Ballast Reduction: Metal halide lamps can reduce cooling load for air conditioned areas when they replace less-efficient interior lamps such as mercury vapor or incandescents. Maintenance Lamp Lumen Depreciation: Decreased light production results in 15-35% less output after 80% of the lamp's rated life. 28 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Cleaning Impacts: Planned cleaning and group reiamping typically results in a 15% energy savings, because fewer fixtures can be used. 2.2.4 High Pressure Sodium High pressure sodium (HPS) lamps, developed in the 1960s as an energy-efficient alternative to mercury vapor lamps for exterior, security, and industrial applications, have achieved widespread use. Standard and deluxe HPS lamps produce a golden-white light. These lamps are useful in applications where high color rendering is a minimal consideration. HPS lamps are the most efficient, commonly used high intensity discharge (HID) lamps, with a life between 10,000 and 24,000 hours. White HPS, available in limited sizes, can replace incandescent, although it has made little market penetration and metal halide is more often used. Aesthetics Lighting Quality: HPS lamps generally have a low color rendering index (CRI), ranging from 9-22 for standard HPS lamps, 65 for deluxe lamps, and 70-80 for white HPS lamps, which produce light more similar to incandescents. Size: Standard HPS lamps range from 35-1000 watts, deluxe versions from 70-400 watts, and white HPS lamps from 35-100 watts. Light Intensity Lumen Output Range: 2,250-140,000 lumens. Ability to Focus Light: White HPS lamps can nearly replicate the incandescents bright near-point source, making these HIDs an energy-efficient option for applications such as 29 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. spotlighting. Other HPS lamps are also near-point sources and provide limited focusing capability. Efficacy Lumens/W att: Standard HPS lamps produce 50-130 lumens/watt, deluxe lamps range between 45-80, and white models between 30-45. Tem perature Impacts: None. Applications Popular Applications: Their reliability and long life make HPS lamps a popular choice for outdoor and industrial applications such as parking lots, roads, airports, warehouses, and some factories. New vs. Retrofit: Kits enable users to convert incandescent or mercury vapor luminaires to HPS, which is often more cost-effective than replacing the entire fixture. Controls • Ballasts: HPS lamps require ballasts. HPS deluxe lamps operate on standard HPS ballasts. Some white HPS lamps operate on standard ballasts, but many use the lamp manufacturer’ s ballast. • Timers: Timers may be used with HPS applications not requiring instant operation. • Occupancy Sensors: Inadequate light during warm-up makes HPS lamps a poor choice for applications using occupancy sensors, although high/low systems may be appropriate. • Dimming: High/low switching is possible when using a special ballast or controller, however, dimming HID lamps typically results in a color shift, making it impractical. 30 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Where dimming is necessary, the lighting system can incorporate a separate incandescent system for that purpose. • On/Off Characteristics: HPS lamps have a 2-4 minute startup time, comparable to metal halide lamps. However, their restrike (hot start) time is 1 -2 minutes—considerably shorter than that of metal halides. An instant restrike HID lamp is also available that contains a second arc tube that starts after a momentary power outage, immediately providing 10-100% of full light. Ballasts that accomplish the same purpose are becoming available. Lighting/HVAC Interactions Savings Beyond Lamp/Ballast Reduction: Because most applications are outdoors, HPS typically offers no HVAC benefits. Maintenance Lamp Failure: Standard HPS lamps fail passively, cycling on and off to signal the end of the lamp's life. Non-cycling models that simply cease to operate are now available in some sizes. Deluxe and white HPS versions indicate the need for replacement by abruptly shifting to a much poorer color. Lamp Lumen Depreciation: HPS lamps lose about 30% o f their initial light level at the end of their rated life. Cleaning Impacts: Planned cleaning and group reiamping typically results in a 15% energy savings because fewer fixtures can be used. 31 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.2.5 Low Pressure Sodium Low pressure sodium (LPS) lamps demonstrate the importance of color in lamp selection. Although LPS are the most efficient lamps available and have lower operating costs than any other commercial light source, their popularity has been limited. At issue is their light's harsh yellow color, which restricts their use to applications where aesthetics are a low priority, such as security and street lighting and general exterior lighting. LPS lamp life ranges between 14,000 and 18,000 hours. Aesthetics Lighting Quality: Emitting a harsh yellow light, LPS lamps have a very low color rendering index. Even street lighting is questionable, as there have been accidents ascribed to the inability to distinguish color. Size: Low pressure sodium lamps range from 18 to 180 watts. Light Intensity Lumen Output Range: 1,800-33,000 lumens. Ability to Focus Light: Low pressure sodium lamps are somewhat tubular, like fluorescents, so the light they produce is not easily directed and controlled. Efficacy Lumens/Watt: LPS lamps are the most efficient light source available, providing 55 to 140 lumens/watt. Temperature Impacts: None. 32 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Applications Popular Applications: Offering high efficiency and very low operating costs. LPS is appropriate for outdoor lighting applications where color and aesthetics are of low concern. These lamps are most often used in street and security lighting. Controls • Ballasts: LPS lamps require ballasts. • Timers: Timers may be used with LPS applications not requiring instant operation. • Occupancy Sensors: Inadequate light during warm-up makes LPS lamps a poor choice for applications using occupancy sensors. • Dimming: Although dimming LPS lamps is technically feasible, their outdoor and security applications make dimming impractical and unnecessary. • On/Off Characteristics: LPS have a fairly lengthy startup time, 10-12 minutes. However, LPS restrike (hot start) time is less than 1 minute. Lighting/HVAC Interactions Savings Beyond Lamp/Ballast Reduction: Because most applications are outdoors, LPS typically offers no HVAC benefits. Maintenance Lamp Lumen Depreciation: LPS maintains 100% of initial lumens, but wattage increases about 7% by end o f life. Cleaning Impacts: Planned cleaning and group reiamping typically saves energy, because fewer fixtures can be used. 3 3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.2.6 Mercury Vapour Mercury Vapor (MV) lamps are the least efficient of all the high intensity discharge (HID) options. They are available in deluxe white and warm deluxe white versions. Clear lamps are also available, but rarely used. Although they have a rated life of more than 24,000 hours, their lumen depreciation is the worst: they lose 30% of their initial light after just 60% of rated life, after which lumen output rapidly depreciates further. Aesthetics Lighting Quality: MV lamps suffer from a low color rendering index (CRI): 50 for deluxe; 15 for clear. Size: Deluxe lamps range from 40-1000 watts; clear versions from 100-1000 watts. Light Intensity Lumen Output Range: 4,200-63,000 lumens. Ability to Focus Light: As with other HID lamps, MV lamps produce a near-point light source offering moderate control capability. Efficacy Lumens/Watt: Deluxe, 30-60 lumens/watt; clear, 30-55 lumens/watt. Temperature Impacts: None. Applications Popular Applications: Because o f their long life, MV lamps have been popular in high- ceiling and inaccessible applications ranging from industrial and commercial lighting to outdoor parking, security, and road lighting. However, MV lamps have become obsolete, 3 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. losing out to more efficient HID lamps. It is sometimes used for occasional special effects, such as “moonlighting”. Controls • Ballasts: Mercury vapor lamps require ballasts; high-quality ballasts are recommended, as voltage fluctuations impact light levels. • Timers: Appropriate for applications not needing instant operation. • Occupancy Sensors: Mercury vapor lamps are not appropriate for occupancy-sensing because they provide inadequate light during warm-up. However, high/low ballasts can provide full lighting during occupied periods and reduced light during unoccupied periods. • Dimming: As with other HID lamps, dimming is commercially available but expensive. Dimming MV lamps also typically results in a color shift, making it impractical. For limited dimming, a separate incandescent system may be more cost effective. • On/Off Characteristics: Mercury vapor lamps cold start in 5-7 minutes and hot start in 3-6 minutes. Lighting/HVAC Interactions Savings Beyond Lamp/Ballast Reduction: When mercury vapor lamps are used in commercial facilities with air conditioning, upgrading from a less-efficient source like incandescent or inefficient fluorescents provides air conditioning savings, in addition to lighting energy savings. Maintenance Lamp Lumen Depreciation: High lumen depreciation makes regular group reiamping of MVs essential for effective lighting. 35 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Cleaning Impacts: Planned cleaning and group reiamping typically results in a 15% energy savings because fewer fixtures can be used. 2.2.7 Light-Emitting Diodes Not true lamps, light-emitting diodes (LEDs) are compact devices that radiate a very small light. LEDs principal advantages are that they offer extremely high efficiency and long life. For example, LEDs available for exit signs use about 1-10 watts and can last up to 100 years, dramatically decreasing energy, maintenance, and replacement costs over the incandescents still often used for this task. A promising market for LEDs in traffic signs is emerging, along with other typical LED applications such as computer displays and control panel indicator lights. Aesthetics Lighting Quality; Essentially monochromatic, LEDs emit light in very narrow and precise wavelengths. They can be tailored to emit red, green, amber, yellow, orange, and blue lights, although red is the most efficient. Size: LEDs operate at very low wattage, generally using from 1-10 watts total in exit sign applications. Light Intensity Lumen Output Range: LEDs are not rated in lumens. They are very dim compared to standard light sources, only about 0.1-1% as bright. Ability to Focus Light: LEDs can potentially focus well, because they’re such a small source, but this quality is not applicable with current products. 36 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Efficacy Lumens/Watt: 0.01-25 lumens/watt. Temperature Impacts: Sudden changes in thermal conditions have little or no effect on LEDs. Applications Popular Applications: LEDs are ideal options for exit signs, computer display, control panels, traffic signals, and signage. New vs. Retrofit: New products are allowing cost-effective, simple replacement o f inefficient, short-lived incandescents in exit signs and traffic lights. Thanks to greatly decreased maintenance costs, payback can occur in less than a year. Controls On/Off Characteristics: LEDs have instant on/off operation; with very long life they're expected to have minimal life-impact from frequent switching. Lighting/HVAC Interactions Savings Beyond Lamp/Ballast Reduction: When LEDs are used in commercial facilities with air conditioning, upgrading from a less-efficient source provides air conditioning savings, in addition to lighting energy savings. Maintenance General: Many LEDs are used in a single exit sign or traffic signal, so the light will function even when some LEDs fail, which makes reiamping flexible. Lamp Lumen Depreciation: LED life span ranges from 5 to 100 years, however not much is yet documented about their lumen depreciation over that time. Preliminary 37 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. information from one manufacturer indicates that effective life may be 6-10 years, after which lumen output may degrade below an acceptable level. 2.2.8 Electrodeless (Induction Lamps) Electrodeless lamps represent a new breed of lamps that produce light by using an electromagnetic field (EF) or microwaves to excite the gas fill in a bulb. The main advantages of these lamps are their long life, ranging from 10,000 to 100,000 hours, and their ability to focus light. Electrodeless lamps are available as either EF induction or prototype microwave sulfur models. Aesthetics Lighting Quality: Electrodeless lamps have a color rendering index of 80+, producing light with a color similar to high-quality fluorescents. Size: EF induction lamps are available in 23-85 watt models; two 6000-watt prototype microwave sulfur units are also in use in the United States. Light Intensity Lumen Output Range: EF induction lamps produce 1,000-6,000 lumens; the 6000-watt sulfur lamp produces 430,000 lumens. Ability to Focus Light: Electrodeless lamps focus light well, because the source is very small; EF induction lamps are targeted to replace 75-watt incandescent reflector (R) lamps in downlights. Efficacy Lumens/Watt: EF induction lamps produce 48-70 lumens/watt; microwave sulfur lamps produce 76 lumens/watt. 38 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Temperature Impacts: Negligible. Applications Popular Applications: EF induction lamps are used widely in Europe, but in the United States limited production by manufacturers has has slowed their popularity. This delay is attributable to a few factors: most models create interference with other electric appliances, induction lamp systems have high first costs, and there is a scarcity of appropriate luminaires. In practice, induction lamps are beneficial in applications for commercial downlighting, display, and wall sconces. Researchers are currently evaluating the effectiveness of using the very powerful microwave lamp in conjunction with a light pipe to distribute light throughout an area. In general, the long life of electrodeless lamps makes them particularly useful where limited accessibility is an issue. New vs. Retrofit: In many applications, electrodeless lamps could replace incandescents and high intensity discharge lamps, offering an exceptionally longer life. Controls • Energizing: Neither the EF induction or microwave sulfur lamps use traditional ballasts. The EF lamp is energized by a radio frequency power supply that runs to an induction coil in the lamp, creating an electromagnetic field that excites the gas fill. In a microwave sulfur lamp, a magnetron generates a microwave field that excites the gas fill in the lamp. • Timers: Electrodeless lamps can easily accommodate the use of timers. • Occupancy Sensors: Electrodeless lamps can be used with occupancy sensors, but users will experience a short lag time between starting and full light output. 39 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. • Dimming: Although dimming is technically possible, dimmable electrodeless lamps are not currently available. • On/Off Characteristics: All versions light instantly, however the interval from switch on to full output ranges from one minute to over eight minutes. Restrike times range between 6 to 15 seconds. Lighting/HVAC Interactions Savings Beyond Lamp/Ballast Reduction: When electrodeless lamps are used in commercial facilities with air conditioning, upgrading from a less-efficient source provides air conditioning savings, in addition to lighting energy savings. Maintenance Lamp Lumen Depreciation: Because electrodeless lamps are a new technology not much information exists about lumen depreciation, however, manufacturers estimate 30% depreciation after 60,000 hours. Cleaning Impacts: As with any lamp, periodic cleaning will help maintain high light output and reduce the number of fixtures needed. 2.3 Lighting Fixtures 2.3.1 Uplights (Indirect fixtures) The principle of Uplighting is simple. Light is directed onto walls and ceiling from a fitting, mounted above eye level, which conceals or screens the light source itself. Most uplighters give a wide symmetrical light distribution: the overall result is that light is softened and diffused, thus theoretically avoiding veiling reflections and glare often associated with many forms of downlighter. Uplighters have been around since 1920s 40 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and 1930s, when they were commonly used in hotels. Fitted with a concealed GLS tungsten source in a crude reflector, they provided an effective way of dramatically highlighting decorative interior features such as cornices or Art Deco murals. But as new, more efficient light sources such as fluorescent lamps, were developed they proved less appropriate for uplighter source. Significant increases in light output demanded proportionately higher wattages, a trade-off, which was unpopular with cost-sensitive managements. However, there has been a fresh burst of interest in re-applying the principles of uplighting to interior spaces. The office, in particular, has benefited; the antiglare requirements of VDT-based technology have given this particular form o f indirect lighting a new lease of life. Today's models can incorporate several types of lighting sources in wattages from 100W to 2.5KW, but most commercial versions use HID high- pressure sodium or metal halide. Uplighters can come in various forms: free-standing or wall-mounted versions are most common, but suspended pendants or troughs are also available. While the primary light source and the type of luminaire reflector are important, the quality and intensity of the light obtained are dependent on the proximity, colour, material and texture o f the surfaces off which the light is bounced. Also, in addition to its potential low-glare capability in VDT-dense workplaces, uplighting can be employed in other ways. Throwing light upwards can help 'raise' a ceiling or enhance the architectural structure or interior design features; or it may be used to boost local ambient light levels. Like all forms of lighting, it is rarely sufficient used in isolation and should be complemented by other forms of task lighting or highlighting. While uplighting can be used as the principal 41 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. overall lighting component, an evenly uplit space can be depressingly bland, and at worst resemble a flat, overcast sky. To summarize: Advantages • Produces little glare or reflection, particularly in VDT- intense environments. • Wide range of luminaire types and styles. • Moderate range of light sources. • Can be integrated into the architecture or furniture. • Free-standing versions are highly portable and adjustable. • Good for creating soft ambient light or boosting local light levels. • Easy installation and maintenance. Disadvantages • Sources generally restricted to HID lamps in commercial luminaires, which can give flicker and colour-shift problems. • Inefficient with unsuitable ceiling or wall finishes. • Free-standing versions are expensive, potentially obtrusive and offer problematic wire management. • Wrong applications can lead to 'hotspots' on ceilings. • Can be unsuitable for split-level environments. Some examples of Uplights: 1. Lytespread Indirect Lighting systems from Lightolier which utilises either the energy efficient 32 Watt T-8 lamp or the 40-Watt biaxial lamp. 42 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 2-4: Antenna uplighter Figure 2-3: Lytespread indirect lighting from Lightolier 2. One of Orgatech's range from Hitech Lighting, the free-standing Antenna uplighter. 2.3.2 Downlights (Direct fixtures) Downlighting is probably the most common form o f lighting in commercial interiors. The principle is simple - the luminaire is located at a high point in the room, usually the ceiling, and the light is directed down to the point where it is needed. Thus direct downlighting can be the most efficient way of lighting a space, at least in terms of putting the maximum lumens per watt onto a horizontal surface, such as a desk or floor. Ceiling-mounted downlighters ( usually fluorescent) are popular in offices because they easily fit the customary modular grid of office designs. They can also be combined with air-conditioning systems. The popularity of downlighting has spun off a massive range o f luminaires for the purpose: there is an almost infinite range of fittings available, in combination with every conceivable type of source. 43 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Downlighters can be discreet or highly decorative: they can be suspended, surface mounted or recessed into the ceiling: and they can incorporate diffusers, reflectors, colour effects and so on. Despite the many advantages of efficiency and flexibility which downlights offer, by their very nature their use can result in one major problem - GLARE. Almost inevitably, the light source is going to be visible. This unfortunate characteristic has been doubly accentuated with the arrival of VDT-based office technology. Downlighting can cause glare on computer screens, particularly if the light distribution is badly planned. Uncontrolled overall downlighting can produce a very flat, featureless, depressing ambience. Also, if downlighters are screened with louvres and reflectors ( to avoid screen glare, for example ) and used as a sole source o f illumination, a 'dark cave' effect may be created. This involves dark ceilings, over-lit horizontal surfaces, poor lighting of vertical surfaces and oppressively heavy shadows on faces. Advantages: • Simplest most efficient method of lighting a space. • Almost infinitely flexible range o f luminaires and lamp combinations. • Standard versions can perform a range of effects. • Can easily fit the modem office ceiling-grid. Disadvantages: • Glare on VDT screens and other shiny surfaces. • Poor vertical illumination. • Used exclusively, can contribute to bland, uninteresting interiors, or the 'dark cave' effect. 44 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. • Wide range o f sources can lead to misapplication or maintenance problems. • Monotonous effect when used in rows on ceilings. • Potential maintenance problems if located in high spaces. Some Examples : 1. Semi recessed RZB from BBI Lighting Figure 2-5: Semi recessed RZB 2. A simple recessed low-voltage downlighter from ILLUMA showing the normaly hidden housing Figure 2-6: Recessed downlight 2.3.3 Tasklighting Tasklighting is local lighting providing illumination directly onto a working area or task. It is almost always used in conjunction with other forms o f ambient lighting in the commercial working environment, although in small-scale or domestic workplaces some people prefer the cocoon-like concentration that dedicated tasklights can offer. 45 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Modem task lights come with a wide range o f light sources, but most commonly they are low-voltage tungsten halogen, GLS or compact fluorescent. With the emphasis on personal controllability they often incorporate local switches and in the case of Iow- voltage versions, dimmers. With this form o f lighting the right quantity of light can be directed exactly where the user wants it. Tasklighting is available in a variety of forms, ranging from free-standing versions to those that are desk or wall mounted, as well as those integrated into overhead storage units. There is a very wide range of styles to fit any interior. Tasklights can be fixed in terms of angle and position (for example small batten fluorescents mounted under the lip of a cupboard or bookshelf), but such an approach negates one o f tasklighting's most important features - personal controllability and adjustability. The widespread use of dedicated tasklighting allows overall ambient light levels within a space, which can save energy. The portability o f tasklighting is also important; when desks are re-configured, the luminaires (either built-in or free-standing) can move too. In general, tasklighting should not be used on its own. a balanced combination of individual tasklights with lower levels o f ambient lighting (possibly from ceiling- mounted fluorescents) can be the most successful form of workplace lighting. Thsi mix also helps to avoid the overall blandness that a single type of lighting produces. Advantages: • Highly controllable and user friendly. • Energy-saving; can entail lower overall ambient light levels. • A wide range of sources and models 46 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. • Highly portable and adjustable. • Can be used to create high local light levels, where necessary. Disadvantages: • Expensive in terms of capital investment. • Requires multiple power outlets. • Plethora of models can lead to problems of aesthetic coherence, and maintenance. • Desk versions can be space hungry. Poor adjustment can lead to irritation for fellow workers. 2.3.4 Tracldights Track-mounted lighting is a popular and well-used lighting system. In essence the track combines a convenient electrical distribution system, where the current, mains or low voltage, runs in an insulated metal sheath inside a supporting metal structure. Using a compatible lamp connector, the current is accessible at any point on the track; lamps can be positioned where required, safety devices ensure that the live track cannot be touched Example: 1. Hitech's cone-tasklight Figure 2-7: Hitech's cone- tasklight accidently. 4 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Track lighting is very flexible. As spotlights are not integral to the track, a combination of different types of lamp can be positioned on one track, tracks are available in both line-voltage and low-voltage versions. The circuit is completed within the track, so power needs to be fed in at one end only; tracks are available in single or multi-circuited versions, so individual lamps or sets o f lamps can be cut to length on site. Most commonly, tracks are straight, but several companies produce curved or angled versions. Tracks are most often installed directly onto ceilings or walls. Where this is too obtrusive, the track itself can be flush with the surface or recessed within the wall so only the lamps protrude. What was originally a functional lighting system can now be used to make a design statement. With the exception of recessed versions, most track systems are, by their nature, obtrusive, which is why in more bland, contemporary interiors, they can often be used to add design texture and focus to a space. Unless care is taken to calculate the total amperage track systems (especially low- voltage) are easy to overload, as more and more spotlights are added over time. Until recently, most companies' tracks and lamps were incompatible with each other, so commitment to a system meant tying into one particular manufacturer. Finally, the very flexibility of the track system can lead to problems. With masses o f spotlights or small floodlights overhead, all of them able to swivel and turn at virtually any angle, it is difficult to avoid some glare at ground level. With units mounted high up on a wall or ceiling, adjustment and maintenance can pose a logistical problem. Advantages • Relatively easy to install. 48 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. • Wide range of track forms and fittings. • Flexible: allows for the combination of lamps o f different types. • High design capability, particularly modem versions. • Safe. Disadvantages • Incompatible with some interior styles. • Large degree of incompatibility between systems. • Used exclusively, can contribute to bland, uninteresting interiors, or the 'dark cave' effect. • Misaligned lamps can cause glare. • Initial equipment costs can be high. Some Examples : 1. An example o f a tracklight used to power many different types of Luminaire Figure 2*8: Tracklight 2. An example o f tracksystem suspended on cables Figure 2-9: T racksystem Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.3.5 Spotlighting The spotlight is a form of lighting where the light beam is controlled in a precise manner, often onto a relatively small area. Spotlights have long been used for dramatic effect in the theatre to focus the audience's attention. The same types of technique are now commonly applied in the commercial sector; many of the spotlights in use either copy the principles of those found in the theatre, or are standard theatre models used without modification. There is a considerable range o f lamp types, lenses, filters and reflectors available; gobos are often used to create illuminated shapes and images on floors and walls. But for reasons of precise optical control, most spotlights still come with incandescent sources, which for commercial applications have a short lamp life and can be relatively inefficient in energy terms. As well as the common track mounted versions, spotlights can also be mounted directly onto walls, ceilings and floors. In terms of power they range from 20W to 1000W, although larger versions are available for specialized applications. The forms of luminaire vary. They are available in a variety o f shapes, colors and sizes, from minimum bare lamp versions, through hi-tech to brass Victorian models. The most common interior application for spotlighting are art galleries, museums, leisure complexes and retail environments. Spotlights are invaluable wherever the designer or architect wants to highlight features or focus a viewer’ s attention on an exhibit, a point-of-sale or product display, for example. Advantages • Highly controllable and user friendly. 50 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. • Energy-saving; can entail lower overall ambient light levels. • A wide range of sources and models • Highly portable and adjustable. • Can be used to create high local light levels, where necessary. Disadvantages • Typically have incandescent lamp source, thus having low lumens/ watt, therefore not good for general lighting. • Expensive in terms of capital investment. • Requires multiple power outlets. • Plethora of models can lead to problems o f aesthetic coherence, and maintenance. • Desk versions can be space hungry. • Poor adjustment can lead to irritation for fellow workers. Some examples: 1. Spotlights from Microlights, which are derived from theatre lighting technology. Figure 2-10: Spotlights from Microlights Figure 2-11: Concord control spot 2. The Concord Control Spot incorporates a framing head, gobo holder, gel holder and adjustable iris head. 51 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.3.6 Linear Lighting Linear lighting systems are recognizable by their continuous tubular form, which is suspended from the ceiling or surface-mounted or recessed. The linear structure carries the necessary electrical and lighting components - wiring, lamps, control gear, louvers, reflecters either within the body, or housed on the outside. More recently, systems have been adapted to carry both communications and data cables. Linear systems come in myriad shapes and sizes. While most original versions had a circular profile, square, oblong and wing-like, aerofoil versions are now available. Linear systems are extremely adaptable; many tubes can be cut to length on site and can be made to change direction, using flexible rubber, plastic or mitred joints. Advantages • Versatile, self-contained and multi-purpose. • Many components and forms available. • Require single power feed and few fixings. • Linear structure makes a strong design statement. • Can serve as a directional device or as a boundary feature. Disadvantages • Complicated to install. • Strong linear form can be obtrusive. • Standard components can be limited. • Limited reflector size can make them inefficient. • Can be expensive. 52 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Example: 1. Linear light detail from Lightolier Figure 2-12: Linear light from Lightolier 2.3.7 Cold Cathode Lighting Cold Cathode is a form of low-pressure lamp which relies on a high-voltage difference (typically 4000-5000V) between two electrodes to create the discharge, rather than heating them, hence the name. Two main types of ionizing gas can be used: argon, which produces light in the blue-green area of the spectrum, and neon gas, which produces red-orange light. Available in a wide range of colors and diameters of tube (typically from 9 mm to 25 mm), cold cathode lighting is almost exclusively custom- made for use as feature and decorative lighting. Colored versions can be bent into all kinds of shapes and are most often used as illuminated signage or as vivid display features to enhance retail or leisure environments. Other uses include edge lighting of buildings or interior architectural features, or hidden lighting behind coves. While the basic sources are relatively inexpensive to produce and do not involve large amounts of dangerous, toxic materials, the one-off nature o f most installations make for high initial investment costs. Advantages • Wide range of colors and diameters. • Can be made up in virtually any shape or form. 53 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. • Tubes are long-lasting. • Low surface temperatures. Disadvantages • Custom-made systems involve high capital investment. • Careful planning required. • High voltages require special installation and safety measures. • Heavy, bulky control gear. • Low light output. • Pronounced flicker. 2.3.8 Emergency Lighting Emergency lighting is a necessary safety requirement for commercial and public buildings. There are, broadly speaking, two types: stand-by and escape lighting. Stand-by lighting is a back-up system, normally involving a separate generator, designed to maintain overall but reduced, lighting levels so that essential work can continue if the mains supply fails. Escape lighting, often powered by batteries, ensures a low level of lighting, sufficient to allow a safe exit from a building via defined escape routes, in a fire or other emergency. Because instant illumination is required, tungsten and fluorescent sources are almost always used in emergency lighting, even if the main lighting is a form of discharge lamp. Power for the system is usually a battery which may be part of the luminaire mounted remotely or located within a central battery room. There are three types of emergency luminaire: 54 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. • Non-maintained versions housing dedicated lamps, which are used only for emergency illumination. • Maintained luminaires, which utilize a lamp which can be used for general lighting, but can be switched over to emergency mode, often at a lower level of illumination. • Combined system (also known as sustained), where a single housing incorporates two lamps, one for standard illumination, the other for emergency Figure 2-13: Emergency lighting 2.4 Lighting Controls Lighting controls vary all the way from simple wall switches to computer controlled ones that can respond to body heat, movement, outside light, and other increasingly complex influences. The aim of such controls, of course is to dim or turn the light on or off in response to need. 2.4.1 Switches This is the simplest form of lighting controls. In some cases, a simple manual switch suffices, but in others some form of remote and/ or automatic on-off switch is needed. A switch controlling a circuit only has two states - on and off - which can be inflexible and hardly makes for a subtle shift in lighting effects. In this the most common method of control is providing switching near the lighted location. Imaginative planning can yield a mastery over the number o f lamps 55 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. operating in each fixture, fixtures per row, whole rows, fractions o f rooms, or any combination thereof. The increased cost of such added switches, wire, conduit, and labor during construction is often quickly offset by lower operating costs due to less energy usage. An increasingly popular switching arrangement is to control one, two or three lamps in a three-lamp fluorescent fixture and two or four lamps in a four- lamp unit. Three way switches in homes, giving control at two room entrances, may not be energy- saving devices in themselves, but they do make life a little easier. Low- voltage control, by which a momentary- contact switch on the wall activates a relay to turn the light on and off, provides an extremely useful design tool. Many lights ( or other electrical devices, including outlets, for that matter) can be activated by switch from one position, or one light from many positions. Low- voltage switching is particularly useful in remodeling projects because thin bell wire usually easier to install, can be used between the switch and fixture instead o f the more expensive 120-V wiring. Rotary switches at one location can be used to control all connected lights or outlets. In the home, such switches can be used to turn on all the lights in the house at one time. 2.4.2 Dimmers Dimmers installed on the wall, in the cord or on the fixture itself furnish versatility in brightness and light level and are also energy savers. Usually manual, it is an almost essential operational control for interiors where lighting has to go off and on regularly - e.g. theatres, cinemas, lecture rooms - and it is becoming more popular in the home, permitting a variety of lighting levels to match different moods. With incandescent lamps, simple phase-control dimmers can be used, small enough to fit into a standard on- 56 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. off switch wall box. Where standard or compact fluorescent lamps are used, the same type of dimmer needs to be supplemented by a transformer feeding the lamp electrodes. Using conventional gear, the fluorescent lamp cannot be dimmed smoothly to extinction: flickering starts at somewhere between 5 and 15 percent of full output. With high- frequency control gear, flicker-free dimming is possible to a much lower level. Installations of high-pressure discharge lamps are not generally amenable to dimming, although variation of the voltage applied to the lamp circuit can provide some reduction in output, perhaps down to 20 percent. 2.43 Timers Timers work as lighting controls to adjust the lighting to seasons and time changes. They are used to turn the lights off and on at predetermined times of the day. In case of ambient lighting which is required only after dark, a solar timer may be used, programmed to adjust the on and off times to take account of changing seasonal daylengths. Automated timers should be capable of being overridden or supplemented manually by staff, within their location, where necessary. Some timers can be reset by a signal from a central location. 2.4.4 Photocells Photocells depend only on the light level, for turning lights on and off, so they are independent of changing seasons. When it gets dark they turn the lights on. The use o f photocells is now widespread and may seem the obvious solution in many installations. But photocells aren't totally ffee from problems. For example, someone has to choose the level at which they are set. If the chosen illuminance is say 500 lux, the 57 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. answer may seem to be to set the photocell to turn off the lamps when 500 lux of daylight is available. This would, in fact, mead that at the moment of switching off, there will be lOOOlux in the space - 500 lux from the daylight and 500 lux from the electric light. A sudden 50% reduction in light levels from lOOOlux to 5001ux can be very noticeable, even distracting. A solution could be to select a higher light level as the switch-off point - say lOOOlux - so that the sudden reduction, from 1500 to 1000 lux, won't be as noticable. However, less energy saving will be realized by maintaining light levels beyond what is strictly necessary. 2.5 Comparisons4 Lamp Type Size Efficacy CRI CCT Life Start ( min. ) Start ( min.) ( Wans) (LPW) ( Kelvin ) (1000 hr) Cold Hot Fluorescent Compact 5-27 25-85 80-85 2700-5000 (9-12 0 0 Full - Size 32-75 55-90 53-90 2700-7500 20-24 0 0 800 mA HO 25-110 50-85 53-90 3000-6500 9-12 0 0 1500 mA VHO 110-215 50-60 53-90 3000-6500 P-12 0 0 Incandescent Standard -1500 5-30 100 2500-3200 .75-5 0 High Pressure Sodium Standard 35-1000 50-130 9-22 2100 16-24 3-4 1-2 Deluxe 70-400 45-80 65 2200 10-15 3-4 1-2 White 35-100 30-45 70-80 2600-2800 10 3-4 1-2 Mercury Vapor Deluxe 40-1000 30-60 50 3300-3900 12-24 [5-7 3-6 Clear 100-1000 30-55 15 5700 18-20 5-7 3-6 4 Boylan. Bernard, The Lighting Primer, Iowa University Press 58 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.6 Calculations This section deals with photometric calculations to quantify light and the related terms thereof. 2.6.1 Luminous Flux Luminous Flux is the light emitted in all directions by a source. Properly called luminous flux or "time rate flow of light", it is measured in lumens (1m). It is denoted by F. 2.6.2 Luminous Intensity Luminous Intensity is the light emitted in a specific direction by a source. Properly called luminous intensity or "flux per solid angle in a given direction," It is measured in candelas (cd). Intensity in a sucesion o f directions is plotted on a distribution curve or polar graph. It is denoted by I. 2.6.3 Illuminance Illuminance is the density of light on a surface. Properly defined as "density of flux incident on a surface measured perpendicular to the surface," it is measured in footcandles or lumens/ ft2. It is denoted by E. So E = F / A where E = Illuminance F = Flux A = Receiving Surface 59 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.6.4 Exitance It is the total quantity of light emitted, reflected, or transmitted in all directions from a surface. Properly defined as "density of flux leaving a surface," it is measured in lumens per square foot (lm/sq.ft.). It is denoted by M. 2.6.5 Luminance It is the accepted term for light that is reflected from a surface in a given direction (back towards the eyes). Properly defined as "intensity of flux leaving a surface in a given direction," it is measured in candelas per square foot (ed/sq.ft.). It is denoted by L. L = E X p or L = E X x where L = Luminance E = Illuminance p = Reflectance (in the case of reflected luminance) x = Transmittance (in the case of transmitted luminance) Methods for Calculating Illuminance from an Electrical Source: There are two most common methods for calculating illumination from an electrical source. They are: a. Inverse Square/ Point Method According to the Inverse Square Law, the flux and resultant illumination is Inversely Proportional to the square of the distance from the source to the surface. Thus E = V d2 60 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. b. where E = Illuminance at the receiving surface I = The luminous intensity at the source when viewed from the direction of the receiving surface d = The distance from the source to the surface however the Inverse square law just gives the amount of light passing through a surface perpendicular to the beam direction at a given distance from a point source. In order to be able to consider non perpendicular surfaces, the point method is based on the addition of the cosine factor to the inverse square law to account for other surface orientations. Thus: E = I cos p/ d2 (This is also known as Abney’s Law) where P = the angle between a line from the source to the surface and a vector normal (perpendicular) to the receiving surface. Note that the inverse square law remains a subset of the equation; where the receiving surface is perpendicular, the cosine is equal to one. The luminous intensity (I) in a given direction is taken from a polar co-ordinate of the fixture intensities, which used to be known as the candlepower distribution curve and now is simply included as a part of a package called the Photometric Test Data. These graphs indicate how much light leaves a source at any given angle from a reference line, typically the axis of the lamp. REFERENCES 1 . Gardner, Cary and Hannaford, Barry, Lighting Design, John Wiley and Sons, Inc. 2. Schiler, Marc, Simplified Design o f Building Lighting, John Wiley and Sons, Inc. 3. Gordon, Gary and Nuckolls, James, Interior Lighting for Designers, John Wiley and Sons, Inc. 4. Sorcar, Prafulla, Architectural Lighting for Commercial Interiors, John Wiley and Sons, Inc. 5. Boylan, Bernard, The Lighting Primer, Iowa State University Press. 6. Steffy, Gary, Architectural Lighting Design, Van Nostrand Reinhold Company. 61 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Part III Considerations for the Web medium The proposed tutorial uses the webmedium. To be an effective tutorial it is essential for it to function as an effective website. More than any other media the web is the easiest platform for anyone to publish or release their work and thus it abounds in good as well as badly presented work. This is because of lack o f user behaviour predictions as a result of it being a new medium. 3.1 Planning Early in the process of creating the web pages, some time should be spent articulating the goals of the document. Web pages can be categorized by purpose. Being responsible to a specific purpose can dictate certain design choices. For starters the website could be catering to one of the following: 1. Providing a user interface to a service 2. Trying to sell products or services 3. Presenting information to an interested audience 4. Providing a collection o f links Lightnet does the third i.e. presenting information to an interested audience. In this case one can safely assume that many of the users will arrive at the site because they need and want the information presented. Hence longer pages can be used, presented in more detail, and worry less about "channel-switching" behavior on the part of the audience. There's a tension between the amount o f "packaging" that is done to the content and the 62 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. user's desire to get the information they need as efficiently possible. What might be a good format for a product advertisement could fail when presenting information documentation because of the frustration incurred when people are forced to navigate and visualize a web of short segments, and are given tantalizing but incomplete glimpses of the answers they need. 3.2 Organization of the Website: There are fundamental rhetorical and organizational reasons for subdividing any large body of information, whether it is delivered on the printed page or in a World Wide Web site. Underlying all organizational schemes are the limitations of the human brain in holding and remembering information. Cognitive psychologists have known for decades that most people can only hold about four to seven discrete chunks of information in short-term memory.1 The goal of most organizational schemes is to keep the number of local variables the reader must keep in short-term memory to a minimum, using a combination of graphic design and layout conventions along with editorial division of information into discrete units. The way people seek out and use information also suggests that smaller, discrete units of information are more functional and easier to navigate through than long, undifferentiated units. Most Web sites contain reference information that people seek in small units. Users rarely read long contiguous passages of text from computer screens, and most people who are seeking a specific piece o f information will be annoyed to have to scan 1 Horton, W. K. 1994. Designing and writing online documentation, 2nd edition. New York: Wiley 63 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. long blocks o f text to find what they are after. Small chunks o f related information are also easier to organize into modular units of information that all share a consistent organization scheme that can form the basis for hypertext links within the Web site. Steps in organizing information Without a solid and logical organizational backbone a Web site will not function well even if the basic content is accurate and well-written. The three basic steps in organizing the information are to divide it into logical units, establish a hierarchy of importance and generality, use the hierarchy to structure relationships among chunks, then analyze the functional and aesthetic success of the material. 3.2.1 Chunking information Most information on the World Wide Web consists of short reference documents that are read non-sequentially. Writers of technical documents discovered long before the Web was invented that users appreciate short "chunks" of information that can be scanned and located quickly. Short, uniformly-organized chunks of information particularly lend them to Web presentation, because: 1. Few Web users spend time reading long passages o f text on-screen. Most users will save long documents to disk, or print them, rather than read extensive material online. 2. Discrete chunks of information lend themselves to Web links. The user of a link usually expects to find a specific unit o f related information, not a whole book's worth of information to filter through. 6 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3. But subdividing the information too much, will frustrate the readers. One to three (printed) pages of information seems about right for a discrete chunk of information on the Web. A link that produces only a small paragraph of information would be silly in most situations. 4. A uniform format for organizing and presenting the information allows users to apply their past experience with the site to future searches and explorations, and allows users to predict how an unfamiliar section of the Web site will be organized. 5. Concise chunks of information are better suited to the computer screen, which provides only a limited view of long documents. Very long Web pages tend to be disorienting, because they require the user to scroll long distances, and to remember the organization of things that have scrolled off-screen. The concept of a chunk of information must be flexible, and consistent with common sense, logical organization, and the convenience of the Web site user. The nature of the content could suggest the best ways to subdivide and organize the information. There will be times when it makes sense to provide long documents in single Web pages, as integrated units of information. Although chunks of information in online documents should usually be kept short, it makes little sense to arbitrarily divide up a long document. This is particularly true when one wants users to be able to print or save the document in one step. The other option is to provide a pdf format document o f the information to let the user print the information in a neatly formatted form, as done in Lightnet. 65 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.2.2 Relationships When confronted with a new and complex information system, users begin to build mental models, and then use these models to assess relationships among topics, and to make guesses about where to find things they haven't seen before. The success o f a Web site as an organization of information will largely be determined by how well the actual organization system matches the user's expectations. A logical site organization C * n fn ii| * n t r im f t a N Figure 3-1: Confusing site layout allows users to make successful predictions about where to find things. Consistent methods of grouping, ordering, labeling, and graphically arranging information allow users to extend their knowledge from pages they have visited to pages they are unfamiliar with. If the users are misled with a structure that is not logical (or there is no comprehensible structure at all), users will be constantly frustrated by the difficulties of finding their way around. 3.2.3 Function After the site has been created, its aesthetics should be analyzed, and the practicality and efficiency of the organizational scheme. No matter what organizational structure is chosen for the Web site, proper World Web site design is largely a matter of 66 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. balancing the structure and relationship of menu or "home" pages and individual content pages or other linked graphics and documents. The goal is to build a hierarchy of menus and pages that feels natural to the user, and doesn't interfere with their use of the Web site or mislead them. Web sites tend to grow almost organically, and often overwhelm what was originally a reasonable menu scheme. WWW sites with too shallow a link hierarchy depend on massive menu pages that over time devolve into confusing "laundry lists" of unrelated information, listed in no particular order: TOO SHALLOW Main menu becomes a massive “laundry list” of unrelated topics Figure 3-2: Shallow site layout Menu pages EBB BUI Menu schemes can also t o o d e e p * * t o ° deeP- buryin8 Menus are numerous and too thin, users are driven information beneath too many through an endless series of nested menus. ssa Content pages layers of menus: Menus lose their value if they don't carry at least four or five links; text or list-based menu pages can easily carry a Figure 3-3: Deep site layout dozen links without overwhelming the user or forcing users to scroll through long lists. Having to navigate 6 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ^ 82 82 through many layers of nested menus before the user reaches any real content is iniuriating and unnecessary. If the Web site is actively growing, the proper balance of menus and pages is a moving target. Complex document structures require deep menu hierarchies, but users should never be forced into page after page o f menus if direct access is possible. The goal is to produce a well-balanced hierarchical tree that facilitates quick access to information BALANCED MENU STRUCTURE Figure 3-4: Balanced site layout and helps users understand how things have been organized. 3.3 Designing Navigation System "Just wait, Gretel, until the moon rises, and then we shall see the crumbs o f bread which I have strewn about, they will show us our way home again. As our fairy tales suggest, getting lost is often a bad thing. It is associated with 2 Hansel and Gretel 68 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57 31 8526 07 ^857 confusion, frustration, anger, and fear. In response to this danger, we have developed navigation tools to prevent people from getting lost. From bread crumbs to compass and astrolabe to maps, street signs, and global positioning systems, people have demonstrated great ingenuity in the design and use of navigation tools. We use them to chart our course, to determine our position, and to find our way back. They provide a sense of context and comfort as we explore new places. Anyone who has driven through an unfamiliar city as darkness falls understands the importance that navigation tools play in our lives. On the Web, navigation is rarely a life or death issue. However, getting lost in a large web site can be confusing and frustrating. While a well-designed hierarchical organization scheme will reduce the likelihood that users will become lost, a complementary navigation system is often needed to provide context and to allow for greater flexibility o f movement within the site. 3.3.1 Building Context With all navigation systems, before we can plot our course, we must locate our position. Whether we're visiting Yellowstone National Park or the Mall of America, the You Are Here mark on fixed-location maps is a familiar and valuable tool. Without that landmark, we must struggle to triangulate our current position using less dependable features such as street signs or nearby stores. The You Are Here indicator can make all the difference between knowing where you stand and feeling completely lost. In designing complex web sites, it is particularly important to provide context within the greater whole. Many contextual clues in the physical world do not exist on the 69 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Web. There are no natural landmarks and no north and south. Unlike physical travel, hypertextual navigation allows users to be transported right into the middle of a large unfamiliar web site. Links from remote web pages and search engine result pages allow users to completely bypass the front door or main page of the web site. To further complicate matters, people often print web pages to read later or to pass along to a colleague, resulting in even more loss o f context. One should always follow a few rules of thumb to ensure that the site provides contextual clues. First, all pages should include the theme/topic of the site. This might be done as part o f the title or header of the page. As a user moves through the levels of a site, it should be clear that they are still within that site. Carrying the graphic identity throughout the site supports such context and consistency. In addition, if a user bypasses the front door and directly accesses a subsidiary page of the site, it should be clear which site he or she is on. Second, the navigation system should present the structure of the information hierarchy in a clear and consistent manner and indicate the location within that hierarchy. This is done in several ways depending on the depth or complexity of the site, as the following examples show: 1. The navigation system for the Figure 3-5: Screenshot of the Argus Clearinghouse site 7 0 1 ! ...... ...» | G 9 B U Y M C Y C L I D __ _ A N D S A V 1 . 1 Q**ArgusClearinghouse imfcnwl fW fiHy — - ■ --f c * -- tncarta-n nfmiU mdlBHUUMSlXWUlU nblbrml rrnionr I « t tfllBTfr llT luinH C kx t + rzr-rzr-rr • - .r. -rr----— i n Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Argus Clearinghouse clearly shows the path the user has taken through the hierarchy and indicates the user's current location. This helps the user to build a mental model of the organization scheme that facilitates navigation and helps them feel comfortable as shown in Fig 3-5. m . ' W C > C N c fc h t* V . y P age GO Auto Specs Ce n t e r s GO > Automotive > Research a car > Specifications > Acura > CL You have chosen Acura CL. [so«crt>caw on» Now chose a style: • 2 3 • 3.0 To p i c s C o m m u n i t i e s S h o p p i n HE M A P I M A l AH by ty|>e S e -r» rr b b y 1 xpert reviews U S E D I A R * N E V / ( A H H UYIM , E N T M U S I A S IS Fast track links Read Automobile Book 1 a u v e a t i » shot of the Infoseek site Figure 3-6: Screenshot of the Infoseek site 2. The above screenshot from the infoseek3 site shows a level pretty deep into the site yet the chances of getting lost is minimized by the simple path flow-text, it also always has the main navigation bar containing the chief divisions o f the site at the top always. These 3 http://www.go.com/?svx=header_logo 71 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. cues help keep the user fully anchored and aware of where he/ she happens to be in the site. Lightnet uses a top navigation bar (which is constant at all levels of the site and enables th euser to jump to any section or the homepage with a single click) and a flow- text at the beginning of each section showing the user how deep he/she is within the site Figure 3-7: Screenshot of lightnet showing navigation path as also the path taken to reach that point. Fig 3-7 show the navigation flow three levels inside the site: 72 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The above screenshot from Lightnet show that for different sections and levels within the site the top navigation bar remains constant, and the beginning o f each section shows the path taken to reach there. Thus Comparisons was reached by moving from the Homepage to Fundamentals and then to comparisons. 3.3.2 Improving Flexibility Hierarchy is a familiar and powerful way of organizing information. In many cases, it makes sense for a hierarchy to form the foundation for organizing content in a web site. However, hierarchies can be fairly limiting from a navigation perspective. In older browsers the user was forced to move up and down the tree, and could not jump across. The Web's hypertextual capabilities removed these limitations, allowing tremendous freedom of navigation. Hypertext supports both lateral and vertical navigation. From any branch of the hierarchy, it is possible and often desirable to allow users to laterally move into other branches. For example, as you explore the details of an incandescent lamp type in lightnet you might want to go and check how it rates compared to other lamp types in the comparisons section. The hypertext link allows you to jump to Comparisons without first retracing your steps back up the incandescent/ lamp types/ Fundamentals hierarchy. It is also possible and often desirable to allow users to move vertically from one level in a branch to a higher level in that same branch (e.g., from a specific lamp type back to the list of lamp types) or all the way back to the main page o f the web site. The trick with designing navigation systems is to balance the advantages of flexibility with the dangers of clutter. In a large, complex web site, the complete lack of 73 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. lateral and vertical navigation aids can be very limiting. On the other hand, too many navigation aids can bury the hierarchy and overwhelm the user. Navigation systems should be designed with care to complement and reinforce the hierarchy by providing added context and flexibility. Lightnet is a medium sized site and care has been taken to provide maximum flexibility without adding confusion by using intuitive clues like an ever-present top navigation bar throughout the site and the path at the top of each page. 3.3.3 Types of Navigation Systems A complex web site often includes several types of navigation systems. To design a successful site, it is essential to understand the types of systems and how they work together to provide flexibility and context.4 a. Hierarchical Navigation Systems Although one may not typically think of it this way, the information hierarchy is the primary navigation system. From the main page to the destination pages that house the actual content, the main options on each page are taken directly from the hierarchy (see figure below). As noted earlier, the hierarchy is extremely important, but also rather limiting. It is these limitations that often require additional navigation systems. The five options at the top of the Lightnet home page constitute the top-level of the hierarchical organization scheme. Note that these icons combine text and images so that users don't have to guess what's hidden behind each. In addition, the imagery and 4 Rosenfield, Louis and Morville, Peter Information Architecture for the World Wide Web 74 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. associated color schemes have been carried through into the appropriate areas o f the Web site, providing both context and consistency. Figure 3-8: Screenshot from Lightnet showing navigation hierarchy b. Global Navigation Systems A global or site-wide navigation system often complements the information hierarchy by enabling greater vertical and lateral movement throughout the entire site. At the heart of 75 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. most global navigation systems are some standard rules that dictate the implementation of the system at each level of the site. The simplest global navigation system might consist of a graphical navigation bar at the bottom/ top of each page on the site. On the main page, the bar might be Figure 3-9: Screenshot of Controls page in Lightnet unnecessary, since it would duplicate the primary options already listed on that page, however Lightnet has it to provide a consistent look. On second level pages, the bar might include a link back to the home page as shown in the figure 3-9. 76 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A slightly more complex global navigation system may provide for area-specific links on third level pages and below. The obvious exception to this rule-based system is that pages should not include navigation links to themselves. The designer to devise the navigation bar to show that you are currently on the main page of that particular section. Designers often leverage a folder tab or button metaphor to accomplish this effect. On Lightnet the color is changed to illustrate that. As can be seen, this type of rule-based global navigation system can easily be applied throughout the entire web site. The navigation system and the graphic design system should be integrated to provide both flexibility and context. Note that the relative locations of the options should remain the same from one version of the bar to another and that, since people read from left to right, Main Page should be to the left of the other options. Both these factors enhance the context within the hierarchy. c. Local Navigation Systems For a more complex web site, it may be necessary to complement the global navigation system with one or more local navigation systems. To understand the need for local navigation systems, it is necessary to understand the concept of a sub-site. This term would identify the recurrent situation in which a collection of web pages within a larger site invite a common style and shared navigation mechanism unique to those pages. For example, a software company may provide an online product catalog as one area in their web site. This product catalog constitutes a sub-site within the larger web site of the software company. Within this sub-site area, it makes sense to provide navigation options unique to the product catalog, such as browsing products by name or format or market. In Lightnet a parallel for such a situation would be Fundamentals being 77 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. one subsite and Calculator being another as they have very different contents, one is theory while the other is mathematical. Each one is independent of the other, but on the same topic thus they are subsites of the main Lighting site. i—Gobal Navigation system at the top ( 1 , > 1 | r^ 1 M I I [ • Rf»' R Dimmers L.Local Navigation system at the bottom Figure 3-10: Screenshot from Dimmers page of Lightnet However, it is also important to extend the global navigation system throughout the sub-site. Users should still be able to jump back to the main page or provide feedback. Local navigation systems should be designed to complement rather than replace the 78 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. global navigation system. In lightnet the global navigation system occurs at the top while the local navigation system occurs at the bottom as shown in figure 3-10. This integration can be challenging, particularly when the global and local navigation systems provide too many options. Alone they may each be manageable, but together on one page, the variety of options may overwhelm the user. In some cases, you may need to revisit the number of global and local navigation options. In others, the problem may be minimized through elegant page design. At no level in Lightnet does the number of options grow so much so as to confuse the user and so integration of the local and global navigation systems on the same page does not create confusing clutter. d. Ad Hoc Navigation Relationships between content items do not always fit neatly into the categories o f hierarchical, global, and local navigation. In practice, this usually involves representing words or phrases within sentences or paragraphs (i.e., prose) as embedded hypertext links. This approach can be problematic if these ad hoc links are important, since usability testing shows "a strong negative correlation between embedded links (those surrounded by text) and user success in finding information. Apparently, users tend to scan pages so quickly that they often miss these less conspicuous links. One can replace or complement the embedded link approach with external links that are easier for the user to see. Embedded Links As you can see, embedded links are surrounded by text. Users often miss these links. One Solution to the Embedded Link Problem is to give links their own separate lines within the paragraph. 79 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Another solution is to create a separate menu of ad hoc links at the top or bottom of the page that point to useful related resources: • Embedded Links • Users One Solution to the Embedded Link Problem The approach one uses should be determined by the nature and importance of the ad hoc links. For non-critical links provided as a point o f interest, embedded links can be an elegant, unobtrusive solution. When using ad hoc links, it's important to consider whether the linked phrase provides enough context for the user. In the following screenshot from the Digital Dissertations Pilot Site, it's fairly obvious where the link will take. However, if 1861 or 1997 were underlined, one would be hard pressed to guess where those links would lead. In designing navigation systems for the Web, context is king. i l M U U W !» H I rr« » m t W i l l - ma w hi * **• » i m t r nm •« M l P t oQ uest' D igital D iss e rta tio n s T h B O M tJ M T a i» Wo b U W s le e e c (n o a »o«»i-. ..... .. __________ M o V it n UNI K h « ie r M |f e a M M ,U M 'i0 c M U ta 9 ^ |n i • f lf e r ittm f tu r a a • 9mm toe twmtmtom IWt fo m a t. ttm f in a iim « ■ M »uiir»(;ai»ii»iiiiatTjatE>ra!ar Figure 3-11: Screenshot of ProQuest Site 80 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. In Lightnet the important embedded links are listed separately at the top o f the page, it occurs in. This does two things: • Makes sure the user does not overlook it in the embedded form • In case of a repeat visit by the user specifically for that link the user need not scroll through copious text to look for it but go through the direct link. Im p o rta n t em b ed d e d links listed on top separately Dimmers Figure 3-12: Screenshot of Lightnet showing embedded links 81 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Part IV: Lightnet: The Web Based Teaching Tool This chapter discusses the functions of Lightnet and how to use it. 4.1 Resources Used and Needed Lightnet uses HTML, Macromedia Director 6, and Javascript to produce files which users can view through the Web. It is meant for students of architecture, interior design or for that matter anyone who wants to get a basic knowledge of artificial lighting. 4.2 Minimum Hardware Using a computer with 64MB Ram or better, 233 MHz. Processing speed. (MMX or Pentium II) Faster machines are recommended, as multimedia scenes will run smoothly on them. 4.3 Software Lightnet needs Netscape Navigator 3.0 or greater or Internet Explorer to run. And also Shockwave plug-in. It has a download center where users can download all the software required for viewing and using the tutorial. To make things better the download center has the whole tutorial in the zipped format which the user can download at one go, and go through the tutorial from his/her hard disk without having to wait for slow downloads. It is specially useful if the user is on a low bandwidth. 82 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4.4 Structure and Organization of Lightnet Lightnet is organized as follows: Opens with a short narrative on lighting, to evoke interest in the subject, it is skippable so that the user does not have to see it on subsequent visits. Then the index page leads the user to two choices: 1. Information Center This section, as the name suggests, gives the user information about using the site. It does three very important and useful things a. Has a plugins and requirements section, which specifies the hardware/ software requirements for using the tutorial, as well as links to where these plugins in softwares can be downloaded. b. Sitemap and navigation conventions followed in the site. c. The printable version o f the entire tutorial in pdf format. d. The download version of the entire tutorial in zipped format. 2. The Tutorial This section comprises of the tutorial and is divided into the following broad categories: a. Fundamentals o f Lighting: This forms the major part of the tool consisting of extensive theory supported by interactive sections to illustrate the concepts of design and decision making in Lighting. It is further divided into: Introduction, Lamp types, Fixture Types, Lighting Controls, and Comparisons. 83 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. b. Interactive Advisor: This section consists of small interactive movies each giving guidelines for lighting up a space. It is categorized by the types of spaces, viz i. Residential: Bedroom, Livingroom. Kitchen, Bathroom, Hallway. ii. Commercial: Showrooms, stores Restaurants, Banks. iii. Offices: Reception, Conference Room, Private Rooms, Open Type Plan, Computer Workstation Areas. iv. Others (schools, hospitals, industrial). c. Calculator This section elucidates the quantitative aspects and measurement of light. It has been set up as follows: The main calculator page has definitions of terms used in photometry and describes the formulae and method for solving lighting calculations. At the end of each method is a link to a small calculator window which calculates the given. Javascript has been used to generate these online calculators. d. Help/Glossary This section has a glossary of technical terms used in the website. It is used in two ways. First, wherever there is a term which requires explanation, the it is linked to the description o f that term in the glossary, this is done by means of anchor links. The whole glossary can also be viewed for general idea and info on various terms used in lighting. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. e. Web Resources Once the user has gone through the tutorial and wishes to get deeper into the subject, he/she now has the required background to understand and gain information from resources which deal with specific aspects of lighting. This section is a pool of web- resources on lighting and has been arranged alphabetically under the following categories: i. Lighting Design ii. Education iii. Lighting related organizations iv. Manufacturers V. Sales and distributors At the top o f the page is a user comments link. And with that the tutorial comes to an end. Following are screenshots from the tutorial in the sequence they are viewed: l i g h t Figure 4-1: Opening shot from Lightnet 85 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. L Figure 4-2: Screenshot o f Index page from Lightnet Information Center UMMIBHIipiQM ■ Iff Wf I99M V C I9r On W» . Unis m ar* end aHBaethat canbatewrtoidortfremjLiflNnethas i been n ijM iiiith a i* tftitpago. This Indbdn a print rnwifin of the . convtoe nta oivnaiddbc also the O ow rO ooaahls vonfiondf thanMesftninitotemafcwtMTOutmdowhtoadttyoialMrddalr and riewthenaarial writhoueworrpno jbotdnetorafc/bandeMh pfittiffli* A ls o * you vdl lo^Jjottbp browserSr ffc o m x ip f other Mrs wtechmttettetnfce, and eiany other cites on the Internet more ■ fOffrtinq «ntf nptuttodfrf th» ' M M tK f I > > w w i>aow jJJJJ .eiey . ^ few tw tor;<fcneiwa«<wUii<et«Nti • Figure 4-3: Screenshot of Information Center from Lightnet 86 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. L i LIGHT.net Figure 4-4: Screenshot of First Page of Tutorial from Lightnet Fundamentals Figure 4-5: Screenshot of Fundamentals Section from Lightnet Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. L Fundamentals Figure 4-6: Screenshot of Introduction Section in Lightnet Fundam entals Figure 4-7: Screenshot of lamps Section in Lightnet Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. L Fundamentals Figure 4-8: Screenshot of Fixtures Section in Lightnet j- Fundam entals Figure 4-9: Screenshot of Comparisons Section in Lightnet Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. L Fundamentals Figure 4-10: Screenshot of Controb Section in Lightnet Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. L D esign Advisor Bedroom Lighting Advis A C C IM T iK jM T IN G Figure 4-11: Screenshot of Advisor Section from Lightnet 91 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. i- o Calculator : . ^ ^ mrbmmmni itia e & e fiB B S 4 S 9 u R K a B a B m z iB iS P Q S S B M K i Figure 4-12: Screenshot of Calculator section from Lightnet 92 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. n h m Figure 4-13: Screenshot of Help/Glossary section from Lightnet Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I ; ^ W eb R esou rces (Links) Figure 4-14: Screenshot of Links section from Lightnet 94 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I Sitemap « * •* » T t a U n u » M t t t i I lwf»r»Mtt«n C —ter • M > N « ( | W « » t ( n | • t m > n < t r t t r r • CalwhM II U O K ttf • f Bndam gnU lp Figure 4-15: Screenshot of Sitemap from Lightnet Figure 4-16: Screenshot of Comments page from Lightnet 95 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Part V Conclusion The Web-Based Teaching Tool on Artificial Lighting has been developed in response to the need for an easy to use tutorial for beginners1 . The environment fulfills the requirements for such a tool because of its graphical vocabulary, which is familiar to the designer, “user friendly” features, interaction, which provides instant response and extensive database. However I would admit that it remains a broad overview, and does not deal with any topic much in detail. But the way this tool has been organized, it can be easily branched out and explore the topics more in detail. And that is made possible by it being a web based tool which allows for hyperlinking that facilitates lateral movement through the information. Thus it can be equally easy to use for a beginner who is looking for basic information as well as for a professional who visits it for in-depth material. Another very useful feature,- which would further enhance the usefulness of this site is a search tool. It would be specially useful for professionals looking for specific information and don’t have the need or time to go through several clicks to reach there. A very useful section o f the site is the calculator section, which describes the quantitative terms in lighting and then calculates results in response to user input. It further enhances the learning process by having some interactive graphics, which explain the results of varying the various parameters o f the calculator. But these graphics are generic in nature. It could be improved upon by providing more dynamic graphics which would change in response to the calculations being carried out from the user input. 1 Students of architecture, interior design, layman. 96 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. According to the author, the site is comprehensive in its present form and serves the needs it is designed for, but the use and need scope could be widened by having the aforesaid additions and enhancements to the tool. 9 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Bibliography Allis, L., Inside Macromedia Director 6 with Lingo, New Riders, 1997 Bartholomew, Robert, Lighting, Color and Space as Factors in Designing Interior Environments, Monticello, III. : Vance Bibliographies, 1980. Bowers, Brian, Lengthening the Day : a History o f Lighting Technology, Oxford ; New York : Oxford University Press, 1998 Boyce, P. R., Human Factors in Lighting, New York : Macmillan, 1981 Boylan, Bernard R., The Lighting Primer, Iowa State University Press, 1987 Burton, Jack L., Fundamentals o f Interior Lighting, Prentice Hall, cl 999 Carlson, Verne, Professional Lighting Handbook, Focal Press, c l991 Egan, M. David, Concepts in Architectural Lighting, New York : McGraw-Hill, c l983 Essig, Linda, Lighting and the Design Idea, Harcourt Brace College Publishers, cl 997 Flynn, John E., Architectural Lighting and Behavior, Vance Bibliographies, 1980 Gardner, Carl, Lighting Design : an Introductory Guide for Professionals, Wiley, c 1993 Gordon, Gary, Interior Lighting fo r Designers, J. Wiley, cl 995 Jankowski, Wanda, Creative Lighting: Custom and Decorative Luminaires, PBC International, c 1997 Leary, Michael, Web Designer's Guide to Typography, Hayden, 1997 Mulder, Steven, Web Authoring Desk Reference: Html, Stylesheets, Javascript, Vbscript, Hayden, 1997 Rooney, William F., Practical Guide to Home Lighting, Bantam/Hudson Idea Books, 1980 Schiler, Marc, Simplified Design o f Building Lighting, Wiley, cl992. Steffy, Gary R., Architectural Lighting Design, Van Nostrand Reinhold, c 1990 Sorcar, Prafulla C., Architectural Lighting for Commercial Interiors, Wiley, cl 987 Turner, Janet, Lighting: An Introduction to Light, Lighting and Light Use, B.T. Batsford, 1994 Web Design Consortium, The Web Design Annual, Books Nippan, 1999 Webster, Timothy, Web Designer's Guide to Graphics: PNG, GIF and JPEG, Macmillan Computer Publishing, 1997 Whitehead, Randall, Residential Lighting: Creating Dynamic Living Spaces, Rockport Publishers, cl993 98 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

Abstract (if available)

Abstract The purpose of this project is to create a Web Based educational teaching tool for Artificial Lighting. This project utilizes the crossplatform web-technology to illustrate the theory and applications o f Artficial Lighting and Design. The aim is to demonstrate the effectiveness of an interactive tool over a textbook in educating lighting concepts. It also has a calculating tool to carry out some basic lighting calculations.

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University of Southern California Dissertations and Theses

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Asset Metadata

Creator Gupta, Madhu (author)

Core Title Lightnet: a Web based teaching tool

School School of Architecture

Degree Master of Building Science

Degree Program Building Science

Publication Date 12/09/2020

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Schiler, Marc (committee chair), Kensek, Karen M. (committee member), Noble, Doug (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c89-412163

Unique identifier UC11666506

Identifier 1397652.pdf (filename),usctheses-c89-412163 (legacy record id)

Legacy Identifier 1397652

Dmrecord 412163

Document Type Thesis

Rights Gupta, Madhu

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA