so that the ratio of their luminances isabout 1.7:1. The resulting illuminanceratio (3:1) is 40 percent lower thanthe typical accent ratio (5:1) found inretail displays, implying that anapproach utilizing the self-luminousmode might conserve 40 percent ofthe energy consumption from typicalaccent lighting practices.As you mighthave already noticed, however, howmuch energy retailers can conservedepends on the reflectance of objectsColorsappearingself-luminousoften stand outand seemto attractour attentionalmostirresistiblyilluminated.Very dark objects will stillrequire high illuminances in order toappear self-luminous.Other factors regarding an objectand its surround, such as the color ofthe object (Ikeda et al., 1993), thecolor of light (Speigle and Brainard;1996), the size of the object (Li andGilchrist, 1999; Gilchrist, et al., 1999),and luminance gradients on theobject and its background (Yamauchiand Uchikawa, 1999) will also affectan object’s luminosity threshold. Infact, these factors might allow lightingdesigners to save additional energy.How Might We Apply TheSelf-luminous ApproachFor Accent <strong>Lighting</strong>?Contour projectors already utilizethe self-luminous approach. A contourprojector tunes its beam patternto the outline of a painting and preventslight from spilling out of anobject by using knife-edged shutters.A recent one uses a film in whichobject outlines are cut out, enablingthe projector to illuminate multipleobjects simultaneously and withmore precision than conventionalprojectors. Since, however, contourprojectors are quite expensive, theymay not always be the best solution.So, it is important to develop lessexpensive ways to utilize and specifythe self-luminous approach. Recentnarrow-beam, sharp-edge accentlighting luminaires may be an alternativesolution.The use of light emittingdiode (LED) technologies might alsofacilitate the self-luminous approach.An accent lighting system composedof a cluster of white LEDs couldmatch a beam pattern to an object’soutline by simply turning on and offvarious LED units to create therequired beam pattern. However, forthose alternative solutions, severalhurdles still need to be overcome,such as:<strong>•</strong> Identifying how precisely theaccent lighting beam should betuned to the objects<strong>•</strong> Identifying how sharp the edgeof the beam should be<strong>•</strong> Identifying how uniform the illuminancedistribution of thebeam should beWhat Is Next?Before applying the self-luminousapproach for practical accent lighting,the questions above should be answered.Then, an appropriate metriccovering the effects of the self-luminousmode on the perception ofbrightness can be established. Oneway might include the definition ofapplication efficacy developed by Reaand Bullough (2001) whereby efficacyis defined in terms of the size of theobject being illuminated. With somemodifications, this metric might beuseful for explaining brightness enhancementeffects in the self-luminousmode. It is also important todemonstrate how much energy wecan conserve through the self-luminousapproach.The significant potentialto realize energy savings fromconventional display lighting certainlywill make this a worthwhile effort.Mark Rea and John Bullough, both ofLRC, contributed to the technical contentof this article.ReferencesAmerican Society of Heating, Refrigeration,and Air Conditioning Engineers(ASHRAE) and <strong>Illuminating</strong>Engineering Society of North America(IESNA), ASHRAE/IESNA Standard90.1-1999, Energy Standard for BuildingExcept Low-Rise Residential Building,1999.Bonato, F., Gilchrist, A.L., The perceptionof luminosity on differentbackground and in different illuminations,Perception, 23, 991-1006, 1994.Bonato, F., Gilchrist, A., Perceivedarea and the “luminosity” threshold,Perception and Psychophysics, 61, 5,786-797, 1999.Gilchrist, A., Kossyfidis, C., Bonato,F., Agostini, T., Cataliotti, J., Li, X.,Spehar, B.,Annan,V., Economou, E., Ananchoring theory of lightness perception,Psychological Review, 106, 4, 795-834, 1999.Ikeda, M., Motonaga, K., MatsuzawaN., Ishida,T.,Threshold determinationfor unnatural color appearance withlocal illumination, Kogaku, 22, 5, 289-298, 1993.<strong>Illuminating</strong> Engineering Society ofNorth America, Recommended Practice2-01, <strong>Lighting</strong> Merchandise Area,2001.Li, X., Gilchrist,A., Relative area andrelative luminance combine to anchorsurface lightness values, PsychologicalReview, 61, 5, 771-785, 1999.Lie, I., Psychophysical invariants ofachromatic color vision IV. Depthadjacency and simultaneous contrast,Scandinavian Journal of Psychology, 10,282-286, 1969.Philips <strong>Lighting</strong>, <strong>Application</strong> GuideRetail <strong>Lighting</strong>, Somerset, NJ, 1991Rea, M., Bullough, J.,<strong>Application</strong> efficacy,Journal of <strong>Illuminating</strong> EngineeringSociety, 30, 2, 73-96, 2001.Simeonova, M., Narendran, N., andBoyce, P.,<strong>Application</strong> of colored LEDsfor retail display windows, Journal of<strong>Illuminating</strong> Engineering Society, 32, 1,52-62, <strong>2003</strong>.Speigle, J., Brainard, D., Luminositythresholds: effects of test chromaticityand ambient illumination, Journal ofOptical Society of America, 13, 3, 436-451, 1996.Uchikawa, H., Uchikawa, K., Boynton,R. M., Influence of achromaticsurrounds on categorical perceptionof surface colors, Vision Research, 29,7, 881-890, 1989.Wallach, H., Brightness constancyand the nature of achromatic colors,Experimental psychology, 38, 310-324,1948.Yamauchi, Y., Uchikawa. K., Luminancelimit of surface color mode perceptionunder spatial luminance gradient,Vision, 11, 1, 1-11, 1999.. . . . . . . . . . . . . . . . . . . November . . . . . <strong>2003</strong> . . . LD+A . . . . 12. . www.iesna.org. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DIGITAL DIALOGUEEmlyn AltmanPHOTO: KEVIN MATHENY, CONSTELLATION ENERGYHERE I AM, WRITING THIScolumn the “analog” way with penand paper. I know what you’re thinking:“Emlyn, why would a computergeek like yourself be using such anantiquated method of writing?” Truthbe told, I’m sitting here cooped up inmy house because Hurricane Isabelknocked out the power all across theregion and I can’t even use the Metroto get over to the office let alone doa simple thing like turn on my computer.I can’t even access my originalcolumn for this issue because it’sstuck in a non-functioning hunk ofplastic and silicone.The worst thing about not havingpower is that my building utilizescomputerized locks for all the apartments.I can’t even leave the apartmentbecause without power, I maybe able to physically walk back up theumpteen flights of stairs using a penlightto guide the way but as soon asI reach the door, my key is just aworthless piece of flat metal unableThe streets of Baltimore, MD, post-Hurricane Isabel.to let me back inside. So here I amfrantically trying to meet my columndeadline with a new article written bywonderful mood-enhancing candlelight.(How romantic.)This accentuates the importanceof “expecting the unexpected” whenit comes to using the computer as adesign tool.You may have taken everyman- and machine-made factor intoaccount when budgeting the time itwill take to complete your project,but when it comes to Mother Nature,Murphy’s Law will always rule. Ialways try to pad my estimated timeof project completion by a day or two(even a week if it’s a long project). Ifeverything goes well then I come outahead of the game; but just that littlepadding has saved my derrière quite anumber of times when faced withconditions beyond my control. I haveexperienced near catastrophes bywater, fire and now wind (combinedwith water). All that’s left now isearth.(Knock on wood!) Thank goodnessI live on the East Coast whereearthquakes are rare.The water experience happenedwhen I was a teaching assistant for acomputer-aided design course atPenn.Working late at the studio withsome of my classmates, we heard thesound of water rushing like a riverwith rapids. We looked around andwater was rushing out of the thirdfloor women’s bathroom,which,coincidentally,wasright across the hallwayfrom our computer labs. Since it wasafter midnight, the labs were closedbut luckily I had the key to get in.While my classmates were busy callingbuilding maintenance and wadingthrough the rapidly rising river huntingto find the shut-off valve, I wasbusy unplugging all the computersand other electrical equipment beforethe water could enter the labs.Fortunately, nobody got electrocutedand the equipment stayed dry. Unfortunately,the architecture facultyoffices on the second floor and theart gallery on the first floor didn’t fareso well. Many a studio art final projectgot drenched.Several years later when I startedworking in Washington, DC, I waspushing on a crunch deadline to finishan animation to show a client the nextday. I was listening to my Walkman,thoroughly focused on the task athand, when in the corner of my eye Isaw the strobe light above my leftshoulder flashing. Little did I know, therestaurant three floors below ouroffice had a fire in the kitchen thatforced the whole building to evacuate.The IT staff quickly grabbed the backuptapes as they left the building butthere was no time for me to do anythingmore than hit “S” to savemy place and hope that the wholebuilding didn’t go up in smoke. Most ofus were frantic because we had noidea if we could get back into thebuilding that day. Luckily, we wereallowed back in the building about fourhours after the fire department putout the blaze, but it still meant that wehad a lot of catching up to do to meetthe client’s deadline the next day.Now, Hurricane Isabel has evokedher wrath upon us. Three days afterthe worst has passed, she leaves inher wake over 1.5 million homes andbusinesses without electricity inVirginia and Maryland alone. In our. . . . . . . . . . . . . . . . . . . November . . . . . <strong>2003</strong> . . . LD+A . . . . 14. . www.iesna.org. . . . . . . . . . . . . . . . . . . . . . . . . . . . .