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1 Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School 2007 Effects of Illuminants and Retail Enviornments on Color of Textiles Fabric Gallayanee Yaoyuneyong Follow this and additional works at the FSU Digital Library. For more information, please contact

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17 Thethreeessentialfactorsthatarenecessaryforcolorperceptionareanobject,an observer,andalightsource(berns,2000;harold,2005a;randall,1998).colorisdescribedby colorsystemssuchasmunsellcolorsystem,naturalcolorsystem,andosauniformscalescolor. Colorismeasuredbothvisuallyandinstrumentally.However,becauseoftheimperfectionsof humaneyessuchasdefectivecolorvision,personalperceptionofcolor,oreyefatigueafter observingbrightcolor,instrumentalcolormeasurementisbecomingmorewidelyusedto overcomethismalady.advancesintechnologyhavegiveninstrumentsanadvantageovervisual colormeasurement(berns,2000).colormeasurementinstrumentshavebeenrefinedoverthe past50years(randall,1998).thefirststandardizedequipmentwasacolorimeterwithlimited measurementoptions,whereasspectrophotometersarecurrentlythemostadoptedcolor measurementequipmentincolorscience(randall,1998). Retailingcompaniesfrequentlybegintheirprocessofapparelproductdevelopmentby identifyingtheseasonalcolor.then,theydesigntheirproducts.becauseofthehighcostof production,apparelisproducedoutsideoftheunitedstatesofamerica(usa).quality assuranceverifiescoloraccuracy(m.hodapp,personalcommunication,march28,2005). Evaluatingcolordifference,communicatingcolorcorrectlyandmakingajudgmentcalloncolor tolerancearecrucialforretailerstohelpincreasecustomerawarenessandtheirsatisfactionof colorqualityintheapparelproduct. Eachcompanyemploysdifferentsystemsforevaluatingcolordifferencesthathave yieldedincompatibleresults.forexample,themunsellsystemcannotpredictthej&pcoats data,thebrown8macadamellipsoidcannotpredictjudd sexperiments,andsoon(berns,2000). Consequently,theInternationalCommissiononIllumination(CommissionInternationalde l EclairageorCIE)ColorimetryCommitteedevelopedCIEL*a*b*(CIELAB)andCLELUVin 1978asguidelinestocoordinateresearchoncolordifferenceevaluation(Robertson,1990).The CIELABhasbeenadoptedandisoneofthemostusedcolordifferenceformulasbytheretail industryformanyyears.thecielabprovidestheretailcompanieswithtwotypesofresults forcommunicatingwithmillsandapparelproducersbothinandoutsideoftheusa:difference inthethreedimensionsofcolor(l*a*b*)andthetotalcolordifference.withthenumerical 1

18 figureofl*a*b*values,ppoducersknowexactlywhatcolorretailcompanieswant.totalcolor differenceisessentialfordetermingcolortolerancebecausethetotalcolordifferenceprovides producerswiththeacceptedcolordifferenceofthesamplesfromtheoriginalcolorstandard. Visualjudgmentwastheonlywaytodetermineshadesortingacoupledecadesago. However,visualjudgmentbythehumaneyelacksreliabilitybecausetheresultscanbeaffected bythetimeofdayandmaydifferwithobservers(harold,2005a).shadesortingisanimportant toolfortextilemanufacturers,apparelproducersandretailingcompaniesinordertohave consistentshadesortedmaterial.whentheirproductsfailtohaveconsistencyinshadesorting,a losstothecompanyisunavoidable.sinceeachfiberhasdifferentabsorbencyability,each specificproductrequiresdifferentspecificationsforshadesorting.therefore,anypass/fail systemcannotapplytoallproducts.becausetheycannotrelyonlyonthepass/faildescription, retailersneedareliabletoleranceforacceptabilityofasamplecolordifferencewhenthatsample willbeusedformultipleapplications(willis,2005). Becausetheretailindustrydoesnothaveaspecificprocedureorsystemforcolor measurementandcolortolerance,eachcompanyselectsitsownproceduretodeterminethese valuesandstandardsforilluminantsfortheevaluationofcolordifferences.whenconsumers considermakingpurchasedecisionsinaretailstore,thelightsourcemaybesignificantly differentfromthestandardilluminantinthecontrolledlaboratorythatwasusedwiththeoriginal apparelofthecolorspecification(hinks,draper,el8shafei,nakpathom,che,&connelly,2000). Inretailstores,irradiance,illuminance,andcorrelatedcolortemperaturesmayvaryonthesame floor(hinksetal.,2000).thevariationsofirradianceandcorrelatedcolortemperaturemeans morethanonetypeoflightingisusedintheretailstore.thevariabilityinilluminanceinthe store,measuredbyafootcandlemeter,indicatesdifferencesinrelationtolightinginstallation. Therefore,thefociofthisstudyweretoevaluatecolordimensionsoffabricsunderdifferent standardilluminants,temperatureandhumidityusedintheretailenvironment(store)andan environmentallycontrolledtextilelaboratory.resultsofthisstudywillprovidetheretail industrywithneededinformationonhowdifferentstandardilluminants,temperatureand humidityaffectthecolormeasurementoffabrics.thisinformationshouldreducethepotential ofreturnedmerchandiserelatedtocolordifferences. 2

19 Purpose Thepurposeofthisstudywastoevaluatetheeffectsofdifferentstandardilluminants withbothportableandtabletopspectrophotometersonthethreedimensionsofcoloroffabrics. Objectivesofthisstudywereto: 1. ExaminetheeffectsofstandardilluminantsasdefinedbytheCommission Internationaldel EclairageorCIE(A,C,D50,D65,D75,F2,F7,F11,TL84and UTL3000)onthreedimensionsofcolor(L*a*b*)ofexperimentalfabrics. 2. Compareilluminancevariabilityinthreekeyareasofaretailstore(purchasecounters, fittingroomsandproductwalldisplays). 3. Determinetheeffectoftemperatureandhumidityonthedimensionsofcolorsin experimentalfabrics. 4. Usingaconsistentgeometryandstandardizationmode,determinetheeffectof portableandtabletopinstrumentsonthedimensionsofcolorsinexperimentalfabrics. TheoreticalFramework OpponentColorTheory Thisstudyevaluatedtheeffectofilluminantsinretailstoreonthethreedimensionsof color:value(l*),redness8to8greenness(a*)andyellowness8to8blueness(b*).forabetter understandingofthisresearch,theopponent8colortheoryofcolorvisionisdiscussed.this theorywasoriginatedbyewaldheringin1878,andwasrefinedbyg.e.muellerin1930 (Harold,2005a).Theopponent8colorstheoryisbasedontheexperimentalevidencethatthereis anintermediatesignalswitchingstageinthehumanvisualsystembetweenthelightreceptorsin theretinaandtheopticnervetakingcolorsignalstothebrain(berns2000;harold,2005a). Haroldstated inthisswitchingstage,redresponsesarecomparedwithgreentogenerateared8 to8greencolordimension (2005a,p.10)andviceversaforthegreen.Forblue,inasimilar mannertheeyesgenerateayellow8to8bluecolordimension(harold,2005a).thewidelyknown symbolsforthetwodimensionsarea*forred8greenandb*foryellow8blue.valueorl*isthe thirddimensionsoftheaxis.thedimensionsofthel*a*b*colorcoordinatesystemareshown infigure1. 3

20 Figure1:Theconceptofanopponent,rectangularcoordinatesystem. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.67.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publication. Illuminants Understandingcolormeasurementrequiresknowledgeaboutlight.Lightisaformof energythatcanbedescribedinwavelengthsandexpressedinnanometersastheunitoflength (Berns,2000;Broadbent,1994a;Harold,2005a).Normally,thehumaneyeissensitiveonlyto visiblewavelengthsbetweenabout400and750nm(1nm=1x10 89 )(Berns,2000;Broadbent, 1994a).Inotherwords,thehumaneyerecognizesthesevenhuesthatrangeinbetween400and 750nm. Manyvisiblelightsourcessuchasthesun,anincandescenttungstenlamp,anda fluorescenttubeareavailable.accordingtobroadbent(1994a),eachlightsourcehasadifferent numericaldescriptionexpressedintermsofspectralpowerdistribution(spd).inaddition,the SPDprovidesinformationaboutthewavelengthortheemittedpower(Berns,2000;Broadbent, 1994a;Harold,2005a).Broadbent(1994a)proposedthatarelativeSPDisenoughforcolor measurement.differentlightsourcesgivedissimilarspdwhichcanbeconvertedto wavelengths.forinstance,daylightisequaltowhitelight,whichcomprisestheentirevisible wavelength.thelightfromanincandescentsourcetendstobemoreorangebecauseithaslower powerintheregionsofgreenandblue. 4

21 Becauselightisimportantforthehumaneyetoseecolor,havingastandardizedlightsource isessentialandcrucialforconsistentandpredictablecolormeasurements.consequently,the InternationalCommissiononIllumination(CommissionInternationaldel EclairageorCIE) definedanumberofspdsorilluminantsforuseindescribingcolor(berns,2000;harold, 2005a).TheCIEselectedmanystandardizedlightsources(Table1)thatareeitherclose replicationsofnaturalsunlight,representcommonlyusedartificiallightsources,orapproximate whitelight(kadolph,1998). Table1 StandardLightSource Type Name Characteristics Ordinaryincandescent LightsourceA Lightfroma5008Wtungsten light CIEilluminantA (CIEILLA) filamentlightbulb Stronginred,orange,andinfrared Noonsunlight LightsourceB CIEIlluminantB (CIEILLB) Typifiesthewavelength compositionofdirectsunlightat noon Stronginyellow Averagedaylight LightsourceD CIEIlluminantD (CIEILLD) Typifiesaveragedaylightoverthe rangeof nm ReplaceCIEIlluminantC(average daylight) Stronginblue Note.From QualityAssuranceforTextilesandApparel,byS.K.Kadolph,1998,NewYork:Fairchild Publications,p.307.Copyright1998bytheFairchildPublications.Reprintedwithpermissionofthepublication. ColorDifferences Acolor8differencespaceis athree8dimensionalspacewithapproximatelyuniform visualspacingintermsofcolor8differencejudgments (Berns,2000,p.71).Berns(2000) elaborated, theyaretristimulusspaceinwhichthetransformationparametersareoptimized usingadatabaseofvisualjudgments (p.71).severalcolor8differenceformulassuchashunter L,a,b,Adams8NickersonL,a,b,CIEL*,a*,b*,CIEL*,u*,v*andCMC(l:c)areobtainable. Inthisresearch,onlyCIEL*a*b*willbeused. CIELAB. 5

22 CIELABis arectangularcoordinatesystemwithaxesofl*,a*andb* (Berns,2000,p. 72).CIELABdefinesthecolordifferencesbetweenastandardandthesamplebytheir differenceinvalue( L*),redness8to8greenness( a*)andyellowness8to8blueness( b*): L*=L*batch L*standard(1) a*=a*batch a*standard b*=b*batch b*standard From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,new York:AWiley8Intersciencepublication,p.72. Moreover,theCLELABcandefinethecolordifferenceintermsoflightness(L*),chroma(C* ab),andhue(h* ab )(p.72): L*=L*batch L*standard(2) C* ab =C* ab batch C* ab standard=(a*batch 2 +b*batch 2 ) 1/2 (a*batch+ b*standard) H* ab =[( E* ab ) 2 ( L*) 2 ( C* ab ) 2 ] 1/2 Source:Berns,2000,p.72. Rationale Randall(1998)definedcoloras thesensationexperiencedorcausedbylightreflected fromortransmittedthroughobjects (p.1).berns(2000)gavethedefinitionofcoloras a certainkindoflight,itseffectonthehumaneye,or(mostimportantofall)theresultofthis effectinthemindoftheviewer (p.1).fromthesetwodefinitions,itcanbeconcludedthat: 1. Threefactorsarenecessaryforhumanstoseecolor:(a)light,(b)anobjectand(c) ahumaneye, 2. Perceivingcolordependsontheobserver, 3. Colorcanhaveascientificperspectiveaswellasaphysiologicalpointofview. Inotherwords,colorismuchmorethansomethingphysical(Berns,2000). Colorselectionofapparelisthefirststepintheproductionperiodpriortoproductdesign, packaging,qualitycontrolandcustomerservice(m.hodapp,personalcommunication,march 6

23 28,2005).Gettingthecolorthatadesignerintendedismorecrucialthanobtainingtheright colortrendfortheseason.manyretailingcompanieseitherhavetheirownin8housecolor qualitycontroldepartmentoroutsourceit.theywouldliketohavethebestandmostaccurate colorfortheirproducts.theyallhave,forexample,acolorsystemforcolormatching,acolor measurementinstrument,trainedobservers,acolorscaleandacolorperceptionsystem.they comparethecolorbetweentheirstandardandtheirproductinordertogetthecolorthattheir designersinitiate.unfortunately,thereisnoawarenessthattheilluminantsintheretailstoreare differentfromthatofthestandardilluminantforthequalitycontrolprocess(azoulay,2005). Moreover,thelightingoftheircustomers householdmightbeadissimilarilluminantfromthe fittingroom,thefloorandthestandardilluminants.thismightcreateacolordifferenceproblem whencustomersinspectthecoloroftheapparelproductsindifferentlocations.asaresult, customersreturnthemerchandise.thisproblemmightbesolvedbymeasuringcolor instrumentallyunderdifferentstandardilluminantsincludingtheilluminantsusedintheretail store.althoughbothportableandtabletopspectrophotometershavebuiltinunitstandard illuminants,thesestandardilluminantsarebuiltaccordingtothestandardofthenational InstituteofStandardandTechnology(NIST)(J.Sylvester,personalcommunication,May21, 2007).ThesestandardilluminantsarealsothestandarddefinedbyCIE.Furthermore,these standardilluminantsincludethestandardilluminantsusedintheretailindustryaswellasthe illuminantsusedontheretailfloor(j.sylvester,personalcommunication,may21,2007). Examiningthedifferencesinthethreedimensionsofcolorsofdifferentstandardilluminantswill providetheretailcompanieswithinformationregardinghowthefabric scolorchangesineach dimensionofcolors.therefore,theretailcompaniescouldestimatethedimensionalchangeof colorsunderdifferentstandardilluminants. Intheacademicrealm,afewstudieshavefocusedoncolorwithintheretailindustry.For instance,collishaw,weide,schambergerandbradbury(2004)utilizedthecmcon02color inconstancyindextoevaluateshadesondifferentsubstances,andofferedalternativeapproaches fordesignersanddyerstominimizemetamerism,andcolorinconsistencecomparedtothetarget shade.jordan(2001)describedsignificantfactorsthatmustbeconsideredinsettingup meaningfulcolortolerancesforbothmanufacturersandtheircustomers.thekeyfindingswere colormeasurement,metamerism,processvariability,shadematchingandspectrophotometers. Hinks,Draper,Che,Nakpathom,El8Shafel,andConnelly(2000&2001)publishedastudy 7

24 showingthelightingvariabilityofoneoffivestoresthataffectcolordifferenceandmetamerism. Hinksetal.(2000)reportedthatthestoreinwhichtheyconductedthestudyhasahighlevelof lightingvariability(variabilityofirradiance,illuminance,andcorrelatedcolortemperature). Hinksetal.(2001)developedtheprotocolformeasurementofarealighting.Thekeyfindingsof thatinvestigationweremetamerism,colorinconstancy,irradiance,colordifferenceandlighting. GalbraithandHardin(1986)designedastudytodeterminetheabilityofconsumerstoperceive smallcolorchangesinfabricbydirectcomparisonfrommemory.forthatstudy,thekeyterms wereconsumerpreferences,colordifferences,colorperception,colorchange,andtristimulus calculations. Manyexpertsinthisfieldincludingdesigners,merchandisers,educators,millspecialists, dyers,qualityassurancemanagersandretailersforesawtheneedofenhancementofthisspecific field.therefore,theconcept2consumercommittee(c2c)withtheagreementofaatcc CommitteeRA36organizedthesurveyresearchinApril2005toexaminetheneedfor developingacolorguidebooktoguidethemanyvariationsofprocessesforcolorcontroltoward astandardizedversionasmuchaspossible(moore,blalock,manalac,revels&hammonds, 2005).Followingalineofinvestigationoncolor,theneedforeducationalresearchrelatedto retailingisnecessaryduetoagapintheliteratureontheeffectsofstandardilluminantsonthe threedimensionsofcolors. ResearchQuestionandHypotheses Thefollowingresearchquestionsandhypothesesweredevelopedwithintheopponent8 colortheoryandwereusedtoguidethisstudy: ResearchQuestionOne Doilluminantsinaretailenvironmentproviderecommendedilluminancelevelsin displayareas,fittingroomsandcashierorcheckoutcounters? RationalResearchQuestionOne Eachilluminanthasdifferentspectralpowerdistribution(SPD).Hinksetal.(2000& 2001)foundthatlightingvariesinaretailstore.Retailindustryutilizesmorethanonetypesof light(azoulay,2005;bell&ternus,2006;hinksetal.,2000;hinksetal.,2001;hoover,1997; Pegler,1998;Pegler,2006).ThestudiesofHinksetal.(2000&2001)showthattherearetwo typesoflightingsinthesamelocation.additionally,thestudyofhinksetal.(2000)istheonly analysisreportingonthevariabilityofilluminanceintheretailstore.however,hinksetal. s 8

25 studyin2000doesnotdiscussthemeaningofthevariationsexcepttoconcludethatthe variationsofirradiance,illuminanceandcorrelatedcolortemperatureshowahighvariationof lightinginthestudiedretailstore.illuminanceisoneofthephotometricqualities(ohta& Robertson,2005).Althoughilluminancelevelsdonotfullymeanbrightness,thelighting engineeranddesignerrecognizethesignificantofilluminanceinretailstore.theilluminating EngineeringSociety(IES)orIlluminatingEngineeringSocietyofNorthAmerica(IESNA) MerchandisingLightingCommittee(1985&2001)recommendsthatlightingorilluminance levelsshouldbemaintainedintheplaneofthemerchandise.eacharearequiresvariationin termsofilluminancebasedonthetypeofstoreandvariousdepartmentswithinthestore.within abuilding,onestoremayincludeallthreetypesofactivityareas:high,medium,andlow.both merchandisingandassociatedareasandsalesandsupportareasencompassallthesethreetypes ofactivity.therefore,frequentchecksonthelevelsofilluminancemustbemadeduetothe flexibilityofspaceuse,regularlychangingdisplaysanddisplayplanes(iesmerchandising LightingCommittee,1985).Inaddition,theIESNAMerchandisingLightingCommittee(2001) proposestherecommendationoflevelsofilluminanceineachareasofdifferentretailstore. ResearchHypothesisOne TherewillbenosignificantdifferencesintheL*,a*andb*valuesofthefabricsbased onthetemperatureandhumidityvariationsinaretailenvironmentcomparedtothestandard environmentallycontrolledconditionsintextilelaboratory. RationalResearchHypothesisOne Temperatureandhumidityhaveacrucialimpactoncolor(Butts2004;Butts2005d; Mooreetal.,2005).AmericanSocietyofTestingandMaterialsspecifiedthestandardpractice forconditioningandtestingtextilesat71±2ºfand65±2%relativehumidity(rh)(2006). EppsandMoore(1989)discoveredthatvariationoftemperaturesaffectthecolordifference. Moreover,theysuggestedtheminimumoffourhoursisrequiredforcolorconditioningin textilesmaterial(1989).anotherresearchconductedbyeppsandmoore(1991)revealedthat deviationsinbothtemperatureandhumidityhaveaneffectoncolorchanging.mooreand colleagues(2005)conductedastudytodeterminebothpracticesandprocessesofindividual companies colorcontrolprocedures.thestudyrevealedthatapproximately60%ofrespondents donotconditioneithersampleorroombeforeconductingbothvisualandinstrumentalcolor measurement(mooreetal.,2005).butts(2005d)concludedinhisstudythatthefluctuationof 9

26 RHfromtheASTMstandardcondition(65%RH)resultedinasignificantcolor difference/change.thiscouldhappeneveninfivepercentvariationinrh.therefore,to minimizecolordifference/changeofthefabric,stabilityenvironmentalofconditionsisessential (Butts,2004d). ResearchHypothesisTwo TherewillbenosignificantdifferencesintheL*,a*andb*valuesoftheexperimental fabricsbasedondifferentstandardilluminants. RationalResearchHypothesisTwo IlluminantsaredefinedbynumberofSPDsforuseindescribingcolor.TheCommission Internationaledel Eclariage(CIE)orInternationalCommissiononIlluminationestablishedthe Standardforilluminantsbasedonphysicalstandardssuchasblackbodyradiatorsorstatistical representationsofmeasuredlight(berns,2000;broadbent,1994a;harold,2005a).some illuminantshavegreatlydifferentspdfromoneanothersuchasfluorescentanddaylight. Azoulay(2005)statedthatsincelightisapartofcolor,changingthelightwilleffectchanging theperceivedcolorofanobject.however,somechangesaremoreobviousthanothers. ResearchHypothesisThree Therewillbenosignificantdifferencesforinter8instrumentagreementorreliabilityinL*, a*andb*valuesbetweenportableandtabletopspectrophotometers. RationalResearchHypothesisThree AccordingtoRandall(1998),spectrophotometershavebecomethemostpopular equipmentformeasuringcolor.nonetheless,thetabletopspectrophotometerhasmany disadvantagessuchaslackofportabilityduetoitssize.therequirementofacleanand controlledenvironmentforproperoperationmakesitproblematicforusers(randall,1998). Randall(1998)proposedthatportablespectrophotometersprovideaspreciseandaccurate measurementsastabletopspectrophotometersintermsofcolormeasurement,andaremore convenienttouse.moreover,reininger(1997)proposedthatoneofthefactorsportable spectrophotometersarerequiredtohaveisaccuracy.hefurtherdefinedaccuracyasinter instrumentagreementwhichmeansanabilityoftwoormorespectrophotometerstoproducethe samevalueswhenmeasuringthesamesample(1997).however,hunterlab(2005b)notedthat inter8instrumentagreementisaverycomplicatedsubject.itisdifficulttobring 10

27 spectrophotometersintoperfectalignment.theapplicationnotesfromhunterlab(2005b) suggestedthatinordertomaximizeinter8instrumentagreementorreliabilityinregardto absolutecolorvaluesmanydifferentspectrophotometersshouldbemadebythesame manufacturerandbesetupusingthesamemodelwithallsixparametersmatching:colorscaleor differenceformula,illuminant,degreeofobserver,instrumentconfiguration,samplepresentation andsamplepresentation.whenseveralspectrophotometersatdifferentlocationsarefollowing thepreviousguideline,thebestinter8instrumentagreementorreliabilitywillresult. Scope Thisstudywillbelimitedinthefollowingways: 1. Thefabricswere100%cottonofplainweavecontstructionwithassimilarfinishesas possible. 2. Theinstrumentalcolormeasurementtoolsemployedweretheportableandtabletop versionsofspectrophotometerswith45/0geometryand10ºobserver. Limitations Thepotentiallimitationsofthisstudyincludethefollowing: 1. Resultsoftheresearchmaynotbegeneralizedtoalltypesoffabric. 2. Resultsoftheresearchmaynotbegeneralizedtootherinstrumentaltypes,geometries andstandardizationmodes. Assumptions Theunderlyingassumptionsofthisresearchincludethefollowing: 1. Theunknowndyewouldhaveanextremeeffectoncolordifference. 2. Noextraneousvariablescontributedtothisresearch. ConceptualDefinitions TheglossarywillbeprovidedinAppendixA.Thefollowingconceptualdefinitionsareusedto guidethisresearch: :Circumferential45 illuminationandnormalviewing(berns,2000.p.85) isathree8dimensionalspacewithapproximatelyuniformvisual spacingintermsofcolor8differencejudgments(berns,2000,p.71).!"#$%:acommonlyusedequationwhichtransformscietristimulus valuesintoathreedimensionalopposedcolorspace(aatcc ) 11

28 &':Attributeofcolorusedtoindicatethedegreeofdepartureofthecolorfromagrayof thesamelightness(berns,2000,p.22). :(a)aspectofvisualperceptionbywhichobjectsarerecognizedbytheir color.(b)inpsychophysicalstudies,visualperceptioninwhichthespectralaspectsofavisual stimulusareintegratedwithitsilluminatingandviewingenvironment(berns,2000,p.27) ($'%:Measurementthatrelatestowhatanobserversees(Berns,2000,p.76). $'%)*Representnaturaldaylight(Berns,2000,p6.). "istheciedaylightwithacorrelatedcolortemperatureof6500k!istheciedaylightwithacorrelatedcolortemperatureof7500k +)$'%*Arangeoffluorescentlampsincludingstandardcoolwhite, full spectrum andtri8band,12intotal(berns,2000,p.6). $:Attributeofavisualperceptionaccordingtowhichanareaappearstobesimilartooneof thecolors,red,yellow,green,andblue,ortoacombinationofadjacentpairsofthesecolors consideredinaclosedring(berns,2000,p.22). $'%*Anumberofspectralpowerdistributionsorilluminantsusedtodescribecolor (Berns,2000,). $'%*Incandescentlightandequivalentstoablackbodyradiatorwithacolor temperatureof2856k(berns,2000,p.6). )%&%'%:Aspectrometerdesignedtomeasurespectralreflectanceortransmittance (Berns,2000,p.83). )%'%:Aspectrometerdesignedtomeasurespectralradianceorirradiance(Berns, 2000,p.83).,$:Attributebywhichaperceivedcolorisjudgedtobeequivalenttooneshadeofgray rangingfromblacktowhite(berns,2000,p.22). 12

29 -.,/ Colorhasbeenusedasasuccessfulsalesstrategyformanycenturies.Customersnotice theseasonchangewhenanewsetofapparelcomesout.forinstance,brightcoloredapparel meanssummerisapproachingwhiledarkercolorsannouncethatthecoldwinterisnowhere. Colorforecastingmovesapparelfashionforwardalongwiththedesigners creativity.to understandhowcoloraffectshumanbeings,manyscholarlyfieldssuchasmarketing, psychology,theaterandtextileshavebeenstudiedintensively.colorresultsfromthe interpretationofourbrainwhenweseethingsunderalightsource;therefore,thethreeessential factorsforhumanstoperceivecolorareanobject,anobserver,andalightsource.inthetextiles andapparelindustries,accuratelydescribingcolorandcolorsystemsisimportant.colorcanbe describedbybothvisualandinstrumentalcolormeasurements.duetothedisadvantagesofthe limitationsofhumaneyessuchasdefectivecolorvision,personalperceptionofcolorandeye fatigueafterobservingbrightcolor,theeyemayhavedifficultyquantifyingcolor(berns,2000). Eventhoughinstrumentsarelessflexiblethantheeye,theyprovidequicklyanumericalresultof appearancethatcorrelateswellwithvisualassessment(hunter&harold,1987).instrumental colormeasurementismorewidelyused,morepreciseandprovidesmorerepeatableevaluations thanvisualcolormeasurement. Colormeasurementinstrumentshavebeendevelopedextensivelyinthelast50years (Randall,1998).Thefirststandardizedequipmentstartedwiththecolorimeterandnow spectrophotometersarethemostusefulandpopularincolorscience(randall,1998).the differencesbetweenthecolorimeterandthespectrophotometerare: 1. Acolorimeterisasimpleinstrumentderivedfromthevisualconceptsofcolor whileaspectrophotometerisahybridinstrumentthatoffersmoreinformationthanthatofthe colorimeter(berns,2000;randall,1998). 2. Colorimetersevaluatecolorimetricquantitiesstraightforwardlybut spectrophotometersanalyzecolorimetricquantitiesfromspectraldata(berns,2000).a colorimetermeasuresonlythethreetristimulusvalues:x,y,zforastandardilluminantwhilea 13

30 spectrophotometermeasuresreflectance,transmittance,orabsorbanceindifferencerangesofthe spectrumfrom wavelengths(Randall,1998). 3. Acolorimetercannotdetecttheproblemofmetamerism,whichresultswhentwo fabricshaveequaltristimulusvaluesbutdifferentspectralpowerdistribution(spd)(berns, 2000),becauseitevaluatesonlythetristimulusvaluesforoneilluminantandoneobserverata time(randall,1998). Spectrophotometershavebeenusedtomeasurecolornotonlyinthetextilesbusinessbut alsoinmanyindustriessuchasprinting,painting,plastic,foodscience,automotiveandsoon. Inotherwords,spectrophotometersareutilizedinanyindustrythatrelatestocolormeasuring. Hence,spectrophotometerssupplytheendusersavarietyoffeaturesandspecifications. Spectrophotometershavetheabilitytomeasurecolorofliquid,textileandpowderforms. Spectrophotometersalsoofferaseriesofcolordifferenceformulasorscales,whitenessindex, illuminants,degreeofobservers,shadesortingandgeometry.also,spectrophotometersrecord thedateandtimeofcolormeasuringandprovideadatalogofitsmemory.moreover,the informationprovidedbyspectrophotometersisdiversesuchasspectralandtristimulusvalues, colorrendering,totalcolordifferences,twoorthreedimensionalgraphandcolortolerance (pass/fail)dependingontheusers purposeofexploitingthisinstrument. Instrumentalmeasurementsresultincolordifferencesfromthestandardandasample thatproducecolortolerancetohelpretailersensurethecolorqualityoftheirproducts.retailers determinethepass/failscopeofthecoloroftheirtextileproductsbasedontheresultsofcolor differencesandcolortolerance(m.hodapp,personalcommunication,march28,2005). Moreover,theoutcomesprovideretailfirmswithanacceptableshadesortingandcolortolerance proceduretouseindevelopingspecificationsforapparelproducts.ciel*a*b*(cielab) color8differenceformulaisacommonformulausedbytheretailindustryforcolormeasurement (Aspland,1993;McDonald,1988;Willis,2005). Thepurposeofthisreviewliteraturewastoprovideaframeworkaswellasestablishthe importanceofthestudy;relatethisstudytothelarger,ongoingdiscussionintheliteratureabout suchstudies,fillingingapsandextendingpriorstudies;andsummarizeresearchstudiesinorder tosharewiththereadertheresultsofotherstudiesthatarerelatedtothisstudy.forabetter understandingofcolorintheretailindustry,thischapterwillincludetheopponent8colortheory, 14

31 howtodescribecolor,spectralpowerdistribution,colorandlight,spectralpowerdistributionof lightsources,standardilluminants,lightinginretailstores,colormeasurementinstrumentsand techniques,colordifference,andcolortolerance. OpponentColorTheory Theopponent8colortheoryofcolorvisionisakeyelementindescribingcolorandwas originatedbyewaldheringin1878andwasrefinedbyg.e.muellerin1930(berns,2000; Harold,2005a).Theconceptofthistheoryisthefourcolorsthatareoppositetoeachother, blue8greenandred8yellow.theopponent8colortheoryisbaseduponexperimentalevidencethat thereisanintermediatesignalswitchingstageinthehumanvisualsystembetweenlight receptorsintheretinaandtheopticnervetakingcolorsignalstothebrain(berns2000;harold, 2005a).Harold(2005a)stated inthisswitchingstage,redresponsesarecomparedwithgreento generateared8to8greencolordimension(p.11) andviceversaforthegreen.forblue,itisthe similarcomparingmannertogenerateayellow8to8bluecolordimension(harold,2005a).both a*andb*arewidelyknownasthesymbolsforthetwohuedimensions:a*isred8to8greenand b*isyellow8to8blue.whilel*isthedimensionoflight8to8dark.thesethreedimensionsofthe colorcoordinatesystemareshowninfigure1.joiningthesethreeconceptsofvalue,hue,and chromacreatesaspherethatorganizescolorintoathree8dimensionalsystemorspace(asshown infigure1). CIELAB Manycolorsystemsweredevelopedtohelppeopleunderstandcolor.Theanalysisofthe Munsellcolorsystemrevealedthattherewereinconsistentchromaticdifferencesforcolorsthat varyinvalue.therefore,researcherssoughttoimprovecolorspacesbasedonthemunsell system.in1942,hunter(berns,2000)developedaconceptofpositioningacolorrelativetothe originbyindicatinghueandchroma.inthesameyear,adamscreatedtheadamschromatic8 valuespaceandbaseditontheheringopponentcolorvisiontheory(aspland,1993;berns, 2000).Aroundthe1950s,NickersonmodifiedtheAdamschromatic8valuespacebyoptimizing constantsfortheirowncolor8differencedata.itwascalledadams8nickersonl,a,boranlab equation.in1973withthecommissioninternationaldel Eclairage(CIE)Colorimetry Committee,MacAdammodifiedtheANLABspaceforaneasiercalculationcalledCIEL*a*b* (CIELAB)(Asland,1993;Berns,2000;Broadbent,1994b;Broadbent,1995).Thepurposeof 15

32 thismodificationwastoimprovetheuniformityofpracticewhenanumberofcolorspaceswere usedforcolorspecification.cielabwillbediscussedagainindetailinthecolordifference equationsection. DescribingColor Describingcolorbyachromaticandchromaticcategoriesillustratesthatcolorisnota linearbutaspherecomposedofhue,valueandchromaaxis.achromaticisblackandwhiteor therangebetweenwhiteandblackthatisexpressedasvalue(americanheritageenglishasa SecondLanguageDictionary,1998).Withthevalueaxis,theseriesforvaluerangesfromwhite, lightgray,gray,darkgrayandblack(figure2).oppositetoachromaticischromaticwhich containsmorecolorandcanbedescribedbyhuessuchasred,green,blue8green,yellow8green, blueandyellow(berns,2000).regardingtheopponent8colortheory,thehueaxiscanbe depictedinfouruniquehues:red,green,blue,andyellow(asshowninfigure1).combining valuewithhue,chromaticcanbeillustratedfromlighttodarkorthesaturationofgrayness (Figure3).Moreover,thechromaticcanbedemonstratedbyhowsaturatedthecolororchroma (Figure3)is.Withasinglehueandwithasinglevalue,thecolorcanbevariedinchroma (Figure4).Insummary,hue,valueandchromaareusedtodescribethecolorofobjects(Figures 5and6)(Berns,2000;Parker,Wolf&Block,2003). Figure2:Theorderofvalue. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.22.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. 16

33 Figure3:Colorswithdifferencecreatedbyaddinggray. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.22.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. Figure4:Colorswiththesamehuecanalsobeorganizedbytheirvalueandchroma. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.23.Copyright2000byJohnWiley&Sons,Inc.Reprintedwiththepermissionofthe publisher. 17

34 Figure5:Athree8dimensionalillustrationofvalue,hueandchroma. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.23.Copyright2000byJohnWiley&Sons,Inc.Reprintedwiththepermissionof publisher. Figure6:Athree8dimensionalcolorcoordinatedsystemcanbedevelopedusingcoordinatesof hue,valueandchroma. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.23.Copyright2000byJohnWiley&Sons,Inc.Reprintedwiththepermissionof publisher. 18

35 SpectralPowerDistribution Whendiscussinglightandcolor,spectralpowerdistribution,SPD,needstobecovered. TheSPDisimportantforbothinstrumentandvisualcolormeasurement.Visuallightis electromagneticradiation(berns,2000;dicosola,1995;sinclair,1997)andlightcanbe describedintermofitswavelengthwherethenanometer(nm)isaunitoflength(berns,2000; Sinclair,1997).Consequently,SPDisusedtodescribelightintermsoftheamountoflight emittedineachwavelength.inotherwords,spdisabasictooltocomprehendlightaswellas colormeasurement. Lightisradiantenergy.Thewordspectrumisusedtodescribetheseparationofthelight intoitscolorcomponentsintheorderoftheirwavelengths(hunter&harold,1987;ohta& Robertson,2005).Thespectrumofradiantenergyisverybroad(Figure7);however,humaneyes canonlydetectasmallportionofthewholespectrumofradiantenergycalledvisibleradiant energy(visibleradiantenergywillbediscussedindetailinalatersection).actually,humansare familiarwithothertypesofradiantenergysuchasultraviolet,x8ray,infrared,microwaveand Radiowave.Lightisfundamentallyaradiantenergythathumanbeingscansee(Berns,2000). Figure7.Thevisiblespectrumanditsrelationshiptootherkindsofradiation(nottoscale). From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.3.Copyright2000byJohnWiley&Sons,Inc.Reprintedwiththepermissionofthe publisher. WavelengthandSPDaretwowaystoillustratelight.Berns(2000)explainedthat radiationcanbeillustratedintermsofwavelengthandwavelengthismeasuredfromonepointto anotherpoint(figure8).moreover,nanometer(nm)isusedasaunitoflengthtodescribelight intermsofwavelength.onenanometerisonebillionthofameter(1/1,000,000,000meter)or about39billionthofaninch(gordon&nuckolls,1995;hunter&harold,1987) 19

36 Figure8.Wavelength. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.3.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. WithSPD,lightisenergywhichispowerxtime.SPDdescribesanylightsourcethat emitsintermsoftheamountoflightoritsrelativepowerateachwavelength(berns,2000). Furthermore,Berns(2000)explainedthatsinceenergyisaresultoftheequationofpowerxtime, ifthepowerofanylightsourceasawavelength sroleisplotted,itwillprovidethepower distributioncurveofthatlightsource(figure9). Therangeofthevisiblespectrumisfrom380to780nm.Eachcolorinthevisible spectrumhasadifferentrangeofwavelengthornanometer.therangeof480to560nmcanbe illustratedintermsofspdaswell.inotherwords,bluecolorcanberepresentedintermsof wavelengthandspdorbycombiningthesetwoterms.anykindoflightsourcecanbe portrayedthisway.forexample,applyingthespdandnanometerofthevisiblespectrumwith typicaldaylight,thegraphcanbeportrayedasshowninfigure9. Inaddition,Figure9illustrateswiththestraightlineoftheSPDcurveat560nmthat daylighthasstableorunityspdat560nm.itmaybeconcludedthatthe spectralpower distributionofasourceisdefinedrelativetoitspowerat560nm (Berns2000,p.3).Light sourcescanbebothnaturalandartificial,forexamplethesun,anincandescentlightbulbanda xenonlightbulb.whenonecommunicatesaboutlight,mostpeoplewillreferencespdand wavelength. 20

37 Figure9.Therelativespectralpowerdistributionornormalizedpowerateachwavelength,for typicaldaylight. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.3.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. Anotherwaytoidentifythecolorofalightsourceisbyitscolortemperature.According togordonandnuckolls(1995),thecolortemperaturedetermines howalampappearswhen lighted (p.44).whenplanckianorblackbodyradiation,agroupoflightsources,isheated,the coloroftheblackbodywillchangeandenergyorheatwillemit.theelectromagneticspectrum oftheemittanceperunitwavelengthcanbeplotted(berns,2000;iescolorcommittee,1990; Sinclair,1997;Wyszecki&Stiles,1967).Theplotvariesandlookslikeacurve.Thesecurves representheatorlightsourcesandalsoareknownasthespdcurvesofheatorlightsources (Sinclair,1997).Whenheated,theblackbodybeginswithdullred8hotcolor.Astheheat increases,thecolorbecomeswhiterandbrighterandsimilartothefilamentintheincandescent lightbulb(berns,2000;essig,2005).thetemperatureoftheblackbodyactuallyisthecolor temperature.forablackbody,thespdanditscolordependonthetemperatureratherthanits composition.theunitofcolortemperatureiskelvin(k)orabsolutetemperaturewhichcanbe obtainedbyadding273tothenumberofdegreesincelsius.colortemperaturedescribesthe chromaticityandnottheactualtemperature.likespdandwavelength,colorshavedifferent temperaturesrangingfromwarmtocool.eachcolorhasitsuniquetemperature.low temperaturesconsistofwarmcolorslikeredandyellowwhilehightemperaturescomprise coolercolorssuchaswhiteandblue8white(iescolorcommittee,1990;essig,2005). The blackbodyradiatoremitsredlightwhenheatedto800k;awarmyellowishwhiteat2800k;a daylight8likewhiteat5000k;abluishwhiteat8000k;andabrilliantblueat60000k (Gordon 21

38 &Nuckolls,1995,p.45).Inotherwords,thelowerthecolortemperatureofthelightsource,the redderthesourcewillbe.inversely,thehigherthecolortemperatureofthelightsource,the blueritwillbe. Correlatedcolortemperatureisusedtodescribethecolorofthelightsourcethatisclose tothecoloroftheblackbodybutdoesnotexactlymatchit(berns,2000;fairchild,1998;ies ColorCommittee,1990;Wyszecki&Stiles,1967).Sinceincandescentlampsresembleclosely blackbodyradiators,theyemitacontinuousspectrumofallofthevisiblecolorsoflight(gordon &Nuckolls,1995).Therefore,thecolortemperatureoftheincandescentspectrumisaccurately specifiedinkelvins.fluorescentandhigh8intensitydischarge(hid)lampsproducea discontinuousspectrumwithblankareaspunctuatedbybandsatspecificfrequencies.essig (2005)furtherexplainsthattheselampsemitmanywavelengthsthatprovidetheappearanceof whitelight,whenseentogether,evenifsomewavelengthsmaybemissing.combiningthese bands,fluorescentandhidgivetheimpressionofwhitelight,byitsapparentorcorrelatedcolor temperature.unfortunately,thecorrelatedcolortemperatureofdiscontinuousspectrumlight sourcesfailstoprovideinformationaboutitsspd(gordon&nuckolls,1995).forexample, coolwhiteandcoolwhitedeluxefluorescentlampshavethesamecorrelatedcolortemperature buttheirspdandtheireffectsoncoloredobjectsandmaterialsaredifferent.gordonand NuckollsalsoaddedthatthislimitationofusingcolortemperaturenotationsalsoappliestoHID sources,includingmercury,metalhalide,andhigh8pressuresodiumlamps(1995). Insummary,SPDisoneoftwomethodsusedtoexpresslightandisausefulapparatusto describethecharacteristicsofalightsource;establishbettercommunicationregardinglight amonglightingengineers,designers,coloristsandsoon;categorizeboththeartificialandnatural lightsourceintermsofstandardilluminants;andgiveadescriptionofcolor.moreover, combiningspdwithcolortemperaturehelpstodefinethepreferredvisualcolorofanylight source.everytypeoflighthasaunique,relativespectralpowerdistributioncurvethatdescribes whatitlookslike,ormoreimportantly,whatotherthingslooklikewhenilluminatedbyit (DiCosola,1995).ByknowingtheSPD,itispossibletoidentifycolor,wavelengthand temperature. 22

39 VisibleSpectrum Theradiatedelectromagneticspectrumhasaverylargeregion,whichcanbedescribedin termsoffrequencyorcyclespersecondandwavelength.thefrequencyandwavelengthare relatedintermsofvelocityorspeed. Thevisiblespectrumisonesmallpartofthetotalradiatedelectromagneticspectrum. Boththevisiblespectrumandradiatedelectromagneticspectrumaredescribedintermsof wavelength.however,thewavelengthregionsinthevisiblespectrumareapproximatelydefined byitsboundaries.forexample,theciestandarddefinestherangeofvisiblespectrumbetween 380and770nmwhileothersourcesdefinethewavelengthofthevisiblespectrumfrom400to 700nm. Besideswavelength,thevisiblespectrumcanalsoberecognizedinhues.Asmentioned above,lightistheradiantenergythatthehumaneyecansee(berns,2000).illuminating EngineeringSocietyorIESColorCommittee(1990)explainedthatlightofasinglewavelength goesintotheeyesystem,thebraininterpretsitasacolor.therearefivedifferenthuesbasedon thewavelengthsoflightassociatedwithnormalcolorthehumaneyecanobserveandeachhue alsohasanapproximatewavelength. Whitelightismadeupoftheentirevisiblespectrum(Berns,2000;IES,1990.When whitelightgoesthroughprisms,itdispersesintoavisiblespectrum.newtowdiscoveredthis factin1730withhisprismsexperiment(figure10). Figure10:Dispersingwhitelightintothecolorspectrum. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.3.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. 23

40 Withintherangeofvisiblespectrum,somewavelengthscanbeseenmoreeasilythan others.thetermwhichdefineshoweasilyhumaneyescanseelightisluminosity.luminosity differsinwavelengths;however,theeyeismostsensitivetolightatapproximately550nmand isalsosensitivetoradiationoutsidethevisiblewavelength(hunter&harold,1987).inother words,humansseelightinthegreenportionofthespectrummuchmoreeasilythanotherparts ofthespectrum.consequently,whencomparingacertainamountofenergyat550nmand650 nm,theeyeismoresensitivetoenergyat550nm.agraphisasimplewaytosummarizethe sensitivityoftheeyetoallwavelengths.luminosityhastwofunctions.thefirstoneiscalled thephotopicluminositycurve.thedaytimeconeorphotopiccurverepresentsthelightness perceptionsaccompanyingchromaticperceptionsatdaytimelevelsofillumination(hunter& Harold,1987;Ohta&Robertson,2005).Thesecondluminosityfunctionforthehumaneyeis calledscotopic.thenightrodorscotopiccurvedescribesthelightnessofobjectsseenatnight, butnottheircolor. Insummary,thevisiblespectrum,theportionofradiantenergythatthehumaneyecan see,containsfivehues.acombinationofallfivehuesresultsinwhitelight.nonetheless,since theluminositydiffersamongwavelengths,theeyeismoresensitivefor550nmorthegreen portioninthevisiblewavelength. SpectralPowerDistribution(SPD)ofLightSources AccordingtoGeneralElectronicCompany(1994),theSPDcurvedemonstratesavisual profileofalightsourceintermsofitscolorcharacteristics.differentsourceswillhavevaried SPDcurvesandtheshapesofSPDcurvesacrossthevisibleregionvarygreatlydueto differencesincolorandtemperature.byreviewingthespdcurve,theusercanidentifywhat kindoflightsourceitisbecausethespdcurveexemplifiestheradiantpoweremittedfromthe sourceateachwavelengthorbandofwavelengthsoverthevisiblesectionfrom380to760nm (GeneralElectronicCompany,1994).Differenttypesoflightsourceshavetheirownunique SPDcurve.Thisdiversityistheresultoftheabsorptionandscatteringprocesswhenlightenters theatmosphere(i.e.ozone,ice,dust,andpollution)(sinclair,1997). ColorandLight Lightisonekindofenergyandoftencoloristheinterpretationofabrainreactingtowhat theeyesees.lightandcolorassistindefiningeachother.colorcanhavemanymeaningsand 24

41 canbedescribedasperceivedcolor,psychophysicalcolorandobjectcolor.illuminating EngineeringSocietyofNorthAmerica(IESNA)statedthat thecolorperceivedasbelongingto anobjectorlightsource,issomethingperceivedinstantaneously (Rea,2000,p.481).The perceivedcoloristheoutcomeoftheintricateinteractionbetweenobjectandlightsource.since threefactors,object,lightandhumaneye,areneededtoperceivecolor,manipulatingthesethree factorsinfluenceshowpeopleperceivecolor. Lightcomingintoahumaneyecausesaphotochemicalreactionintheretina.The photosensitiveneuroepitheliallayersconsistoftwotypesofcell(berns,2000;ohta&robertson, 2005).Thesetwocells(rodsandcones)detectlightintensityandcolor(Berns,2000;Ohta& Robertson,2005;Parker,Wolf&Block,2003).Indarkenvironments,therodswillperceivethe brightnessordarkness.inbrightenvironments,theconeswillperceivecolor.whenthecones alonefunctioninbrightenvironment,itiscalledphotopicvision.whenbothrodsandcones functiontogether,itiscalledmesopicvision.inaddition,scotopicvisioniswhentherodsalone functioninrelativetothedarkenvironment(ohta&roberston,2005).accordingtoparker, WolfandBlock(2003),thelevelsofillumination(highandlow)affecthowhumansseecolor sincethehumaneyes sensitivitytohighorlowlevelsofilluminationaredifferent.therods, whichactivateinnightvisionorlowlevelsofillumination,aremostsensitivetowavelengthsin thegreen8bluerangewhilethecolor8sensitiveconesaremoreresponsivetotheredandgreen wavelengthsoflightathighlevelsofillumination(parker,wolf&block,2003).sensitivityof theeyestotherodsinfluencestheeyestoseecolorunderthelowlevelsofilluminationwitha greenish8bluecasttoallhues(parker,wolf&block,2003). AccordingtotheIESNAlightinghandbook(Rea,2000),psychophysicalcolorisdefined as thecharacteristicoflightbywhichanobservercandistinguishbetweenpatchesoflightof thesamesize,shapeandstructure (p.481).colorcouldbediscussedintermsoftheresultof theamountofenergyorradiantpoweratdifferentrangesofvisiblewavelengthfrom380nmto 780nm(Rea,2000).Objectcolorcouldbedescribedaswhatpeopleseebecauseoflightthat eitherreflectsortransmitsfromanobjectthoughhumaneyesandthehumanbraininterpretsthe color(rea,2000).eventhoughlightisnecessaryforhumanbeingstoseecolor,sometimeslight caninfluencehumanstoperceivethewrongcolor.thisoccurrenceiscalledilluminant metamerism. 25

42 Colormaterialsreflectdifferentlyineachwavelengthorilluminant(IESColor Committee,1990).ThereflectanceofcolormaterialscanbeplottedontheSPDcurve. Materialsmayreflecthigherorlowerpercentagesunderdifferentlights.Forexample,ablue materialmayreflectahigherpercentageofbluelightthanredlight(iescolorcommittee,1990) oralemonviewedunderabluelightmaylooklikealime(berns,2000). StandardIlluminantsandStandardSources(forcolorimetricassessment) Sincethesameobjectseenindifferentlightsources(i.e.incandescent,daylight,and fluorescent)resultsindissimilarcolor,researchersareawareofselectingilluminantstoevaluate color.thiscreatesaneedforstandardizinglightsourcesforspectralpowerdistribution.the CIEsolvedthisproblembydefiningtheSPDtousefordescribingcolor.TheCIEutilizedeither thephysicalstandardusingblackbodiesorstatisticalinformationinmeasuringcolorto categorizeeachilluminant.accordingtoberns(2000),anilluminantis lightdefinedbya relativespectralpowerdistributionthatmayormaynotbephysicallyrealizableasasource.ifa sourceisavailableinaphysicalform,itbecomesastandardsource (p.6).consequently, standardilluminantsandstandardsourcesaredistinctbyphysicalform.astandardsource actuallyhasaphysicalform.berns(2000)elaboratedthatthespdofthesourcewhichis physicallyrealizablelight (p.6)canbedeterminedbyexperiment.whenthespdofthat sourceisspecified,thatsourceturnsintoastandardsource.inaddition,dicosola(1995) explainedthatasourceisanactualphysicallight,somethingthatcanactuallybeturnedonto illuminatesomething;however,anilluminantisalightthathasbeendefinedbyaspd,butmay notactuallyexist. Standardilluminantsareasfollows: 1. IlluminantArepresentsaPlanckianradiatorandisusedasacolorimeter calculatorwhenincandescentilluminationisofinterest.itisequivalenttoablackbodywiththe colortemperatureof2856k. 2. IlluminantBrepresentsdirectsunlight.Itscorrelatedcolortemperatureis4874K (Hunt,1998).AccordingtoHarold(2005a),comparedtoDseriesilluminants,thisilluminant doesnotprovideacompleteandaccuratenaturaldaylight.hunt(1998)addedthatnowthe standardilluminantisconsideredtobeobsolete. 26

43 3. IlluminantCrepresentstheaveragedaylightfromthetotalskyoradaylight simulator.illuminantcisthespdofilluminantaasmodifiedbyatwo8celldavis8gibson liquidfilterdefinedbycie(berns,2000;fairchild,1998;wyszecki&stiles,1967).the correlatedcolortemperatureofilluminantcis6774k(fairchild,1998;hunt,1998).however, illuminantcisapoorrepresentativeofnaturaldaylight(berns,2000;harold,2005b).in addition,hunt(1998)addedthatbothbandcilluminantshavetoolittlepowerintheultra8 violetregion.thus,thisilluminantisnotrecommendedforuseincolormeasurement. 4. IlluminantD:AseriesofDilluminantsrepresentnaturaldaylightdefinedina waythatallowsalargearrayofcorrelatedcolortemperaturetobeanalyzedintermsofspd (Berns,2000;Fairchild,1998).BothD65andD50havebeenstatisticallydefinedbasedupona largenumberofmeasurementsofrealdaylightinmanyplaces(fairchild,1998).thedseries illuminantsarerecognizedbythefirsttwodigitsoftheirtemperature.forexample,d65and D50areCIEaveragedaylightwithacorrelatedcolortemperatureof6500Kand5003K respectively.someindustriessuchaspaints,plastics,andtextilesemployd65butthegraphic artandcomputerindustriesutilized50(berns,2000).haroldstatedthatthedseriesoffersa completeseriesofnaturaldaylightfromyellowtobluecolortemperature.hence,itsupplies morecompleteandaccuratenaturaldaylightthantheilluminantsbandc(2005).fairchild (1998)addedthattheDilluminantscanbeeasilycorrelatedwithcolortemperature. 5. IlluminantF:AseriesofFilluminantsrepresenttypicalSPDswitharangeof fluorescentsources,includingstandardcoolwhite,warmlight,fullspectrumandtri8band.the serieshasatotaloftwelve:f1tof12(table284).thesetwelvelampscanbecategorizedinto threegroups:normalorstandard(f1tof6)(table2),broadband(f7tof9)(table3)and threeband(f10tof12)(table4)(hunt,1998).thenormalrangehasbeendesignedforhigh efficacyandadequatecolorrendering(butnotforthereddishcolors,sincesomedeficiencyin emissionoccursatthelongwavelengthendofthespectrum).hunterlab sapplications commentonequivalentwhitelightsourcesandcieilluminantsnotesthatthef2isthemost indicativewithinthisgroup(2005a).thebroadbandhasbeendesignedtosolvethedeficiency inemissionatthelongwavelengthendofthespectrum;therefore,ithasgoodcolorrendering. Itsproblemislowefficacy.Thethreebandhasbeendesignedtoemitfromthethreenarrow bandsofthespectrumatapproximately610,545and435nm.so,ithasrelativelyhigh efficaciesandfairlygoodcolorrendering(hunt,1998).threedistributions(f2,f7andf11)are 27

44 intendedtobeusedwhenthechoicewithineachgroupisnotcritical(hunt,1998).table284 presentnotonlythecienameforthefseriesbutalsothecommonnamesthatareusedinthe luminaryindustry. Table2 StandardFluorescentIlluminants CIEilluminant Correlatedcolortemperature Commonname(s) F1 6403K Daylight F2 4230K CoolWhiteFluorescent F3 3450K White F4 2940K WarmWhite F5 6350K Daylight F6 4150K LiteWhite Sources:EquivalentwhitelightsourcesandCIEilluminantsbyHunterLab(2005b) Table3 BroadbandFluorescentIlluminants CIEIlluminant CorrelatedColorTemperature CommonName(s) F7 6500K D65Daylight F8 5000K D50 F9 4150K CoolWhiteDeluxe Sources:EquivalentwhitelightsourcesandCIEilluminantsbyHunterLab(2005b) Table4 NarrowTribandFluorescentIlluminants CIEilluminant Correlatedcolortemperature Commonname(s) F K TL85,Ultralume(UT) 5000 F K TL84,SP41,Ultralume (UT)4000 F K TL83,Ultralume(UT) 3000 Sources:EquivalentwhitelightsourcesandCIEilluminantsbyHunterLab(2005b) 6. IlluminantEortheequal8energyilluminantisoftenofmathematicalutility (Fairchild,1998).ItisdefinedashavinganSPDof100atallwavelengths. AmongallCIEilluminants,onlyilluminantsAandCcanbelabeledasstandardsources becausetheyaretheonlyonesthathaveaphysicalsourcethatisanincandescentfilamentlamp. However,illuminantsA,CandFseriescanbereproducedtoreplicatethestandardsources. 28

45 TherearemanysourcesdesignedtoreplicatedaylightbuttheydonothavethesameSPDasreal daylightalthoughalabelsignifiesdaylightord65. Asmentionedearlier,thecolortemperatureofanilluminantprovidesinformation regardingchromaticitynotitsrealtemperature.eachstandardilluminanthasitowncolor. Table5suppliesinformationonCIEstandardilluminantsA,CandDseries,relatedtocolor temperature,colorandapplication. Table5 TheRepresentation,ColorTemperature,ColorEnergyandApplicationsofCIEStandard Illuminants Illuminant Representation Color temperature Color energy Application A Incandescentor tungstenlight source 2856K Yellowish/red Home C Averageornorth 6774K 8 Almostobsolete skydaylight D50 Horizonlightor warmdaylightorat sunriseorsunsetor equalenergy 5000K White Evaluatingcolor uniformqualityin thegraphicarts industry daylight D55 Mid8morningor mid8afternoon 5500K 8 8 D65 D75 daylight Noondaylightor Averagedaylight Overcastdaylight ornorthsky daylight 6500K Moderateblue Generalevaluation ofcolor,color matching applicationsof paints,plastics, textiles,rawinksand othermanufactured products 7500K Moderateto deepblue Generalevaluation ofvisualevaluation ofopaquematerials asoutlinedby ASTMD1729 Sources:EquivalentwhitelightsourcesandCIEilluminantsbyHunterLab,(2005b);Explanation ofvariouslightsourcesandtheiruseinvisualcolormatchingapplicationsbygtigraphic Technology,(2007);IlluminanttypesbyXrite,(2006). 29

46 ColorRenderingIndex(CRI) TheInternationalCommissiondevelopedthecolor8renderingindex(CRI)in1970. Colorrenderingofalightsourceis theeffectthesourcehasonthecolorappearanceofobjects incomparisonwiththeircolorappearanceunderareferencesource (Judd&Wysecki,1975,p. 364).Althoughsomelightsourcessuchasthedaylightfluorescentmayhaveexactlythesame chromaticity(i.e.correlatedcolortemperatureanddepartureofblackbodylocus)assomephase ofnaturaldaylight,theirspdsaredifferent(macadam,1981).therefore,whenamaterialis illuminatedbybothadaylightfluorescentandnaturaldaylight,thecoloredmaterialwillhave differentchromaticities(i.e.x,ycoordinates)(macadam,1981).juddandwyszecki(1975) foundthatdifferencesinspdswillmakeobjectsilluminatedbytheartificiallightsourceappear tobeadifferentcolorfromthoseperceivedundernaturaldaylight.consequently,fairchild (1998)thisisverysignificantintheengineeringofartificialilluminationandthechoiceoflight sourcesfordifferentinstallations. TheCRIiscalculatedfromthespectralreflectanceofasetofeightmoderatelychromatic materials(macadam,1981)andthecrirangeisfrom0to100.acriof100indicatesno differencesoranexactmatchofallofthechromaticities.lightsourcesareevaluatedrelativeto referenceilluminantswhicharethecied8seriesofilluminantsforcorrelatedcolortemperature lessthanorequalto5000kandplanckianradiatorsforcorrelatedcolortemperaturelessthan 5000K(Fairchild,1998).Areferenceilluminantischosenwhichhasthesamecorrelatedcolor temperatureasthetestsource. TheCRIistobeusedasatoolforpeopletohave anideahowalightsourcewillrender colorscomparedtoarbitrarylightsourcesinuseatthetimeitwasdeveloped (Thiry,2004,p. 36).However,confusionexistsrelatedtousingCRIincommerciallightingcompanies,andthe retailindustry(hoover,1997;judd&wyszecki,1975;thiry,2004).theconfusionisthateven thoughthecridoesnotofferadequateinformationtoevaluatethecolorrenderingpropertiesof variouslamps,theretailersandcommerciallightingmanufacturersuseditasifitwere(hoover, 1997;Thiry,2004).Hoover(1997)statedthatwhilecorrelatedcolortemperature(CCT)andthe CRIvaluearederivedfromSPD,thisinformationdoesnotprovidefortheuniquecharacteristics ofsources.thecctandcricannotspecificallypointoutdifferentlightsourcesunlessthe SPDisconsidered(Hoover,1997).Moreover,theweaknessesoftheCRIare1)ifthevalueof 30

47 XE,whichisacomponentintheequationofCRI,issmall,itatbestindicatesonlythecolor differenceand2)thexeprovidesonlythequantityofcolordifferencenotthedirectionofthe shadeshift(hoover,1997).juddandwyszecki(1975)notedthattherangeofcrialsocreates misunderstandinginapplyingthecritogradesources.differentcommerciallighting companiesconsiderdifferentratingsofcri(rangingfrom50880dependingoncompany)as indicatorsofgoodcolorrendering.juddandwyszecki(1975)statedthataveryhighgeneral CIEcolor8renderingindex(95ormore)isrequiredforacriticalexaminationofcoloredobjects. RetailLighting Lightandcoloraretwoconceptsthathavebeenstudiedbymanyareas.Intheretail industry,coloristhefirstthingthatdrawsacustomer sattentiontoaproduct(azoulay,2005; Hoover,1997;Rea,2000).Sincecolorisnotonlywhathumanbeingsperceivebutcan influencehowapersonfeels,manipulatinglightingisaverysignificantwaytoenhancesales activity.azoulaystatedthat lightingisasmuchasalescomponentofagarmentontheretail floorasthefabricis (2005,p.44).Thelightingsystemcouldcreateapleasantandsecure environment(theilluminatingengineeringsocietyofnorthamerica(iesna)merchandise LightingCommittee,2001).Itisachallengeforthemanagementteamtoutilizethelightingin suchawaythatcreatesanatmospherethatinitiatesandcompletesthesaleaswellasbeingcost efficient.in2002,heschong,wrightandokuradirectedresearchtoevaluatetherelationship betweenthepresenceofdaylightandsalesinretailbuildings.theconclusionoftheoutcome foundthataddingskylightstotheaveragenon8skylitstorewouldlikelyimprovesales performanceby40percent(withtherangeof31to49percent). AccordingtoIlluminatingEngineeringSocietyofNorthAmerica(IESNA)Lighting Handbook(Rea,2000),therearethreegoalsforretaillighting:attractthecustomer,allowthe customerstoevaluatethemerchandiseandfacilitatethecompletionofthesale.lightingshould attractthecustomer,evenattheentranceofthestorepersuadingthepotentialcustomertocome in.furthermore,lightingcandrawthecustomertowardthemerchandiseinthewindowdisplay. AccordingtotheIESNAMerchandiseLightingCommittee(2001),thefactorsthatassista successfulsalearethequantityandqualityofillumination,theimpressionitcreatesaboutthe merchandise,andtheeffectithasontheretailarea sappearance.buyingdecisionsareinitiated assoonasthecustomerisvisuallyattracted.therefore,tofacilitatedecisions,lightingshould 31

48 allowthecustomerstoevaluatethemerchandise.appropriatelightinginthefittingroomaswell assalesareasisverycrucialformerchandiseevaluation.theseareasareoftenwheredecisions aremade.lightingshouldfacilitatethecompletionofthesalesincethatiswhatcountsfor accomplishingbusinesstransactions.itisnecessaryfortheretailertoensurethatcustomersare abletolocatethecashiercounters,thatsalesrepresentativeshaveproperlighttoprovidegood servicefortheircustomersandareabletoseewhatthecustomerseeswhentherearequestions aboutcolor,fabricorproduct.itisappropriatetoconcludethatlightingassiststhewholesales transaction. CharacteristicsofLightandLighting Understandingthecharacteristicsoflightandlightingwillallowthelightingdesignersin theretailindustrytogeneratethedesiredvisualimpression.knowledgeof(a)illuminanceand luminance,(b)reflection,refraction,transmissionandabsorptionand(c)colorinthestore environmentarenecessaryforcreatingthisimpression. IlluminanceandLuminance. Illuminanceorincidentlightis themeasureoflightthatisfallingontoanobjector surface (IESNAMerchandisingLightingCommittee,2001,p.4),expressedinluxor footcandles.alightmeterisusedtomeasuretheilluminanceleveltodeterminethe acceptabilityofalightinginstallation.onemeter8candleisequivalenttoonelux(ohta& Robertson,2005).However,thehumaneyedoesnotresponsetoincidentlight;itrespondsto luminanceorlightthatisreflected.theiesnamerchandisinglightingcommittee(2001) definedluminanceas photometricbrightness (p.4).inotherwords,luminancesignifiesthe intensityperunitareaofanilluminatedobjectorsurface.theunitofluminanceis candelas/meter 2 orcandelas/foot 2.Todeterminethephotometricofbrightnessofthe merchandise,aluminancemetermustbeutilized. Furthermore,theIESNAMerchandisingLightingCommittee(2001)suggesteda guidelineforlightingdesignersbystoreclassificationscalledthelightingdesignguide.the lightingdesignguideratestheimportanceofdesignissues(includingilluminance)basedupon differentareas,locations,andtasks(table6).becausethisresearchfocusesonapparelproducts, thesummarytableofthevalueofilluminancebothhorizontalandvertical(below)provides informationonlyfortheselectedareasofaretailstorethatrelatetoapparelproducts. 32

49 Table6 TheValueofIlluminancebothHorizontalandVerticalforSelectedRetailStoreAreas Retailstoreareas Illuminance horizontal [Lux/footcandles(ft)] Illuminance8vertical [Lux/footcandles(ft)] Alterationroom 500/50 300/30 Fittingroom 8 Dressingareas 8 Fittingareas 300/30 500/50 50/5 300/30 Lockerrooms 100/10 30/3 Stockrooms,wrappingand packaging Salestransactionareas Circulation Generalmerchandise presentation Featuredisplay Showwindow 300/30 50/5 300/ / / ,00085,000/ ,000/100 Reflection,Refraction,TransmissionandAbsorption Merchandisemayreflect,refract,transmitand/orabsorblight.Eachapparelproductmay reacttolightdifferentlybaseduponmanyfactorssuchasdyetype,textiletextureandfiber content.knowinghowmerchandisereactstolightinfluencesdecisionsofilluminance, luminanceratios,lightsourcechoiceandluminariesselection(iesnamerchandisinglighting Committee,2001). ColorandtheStoreEnvironment Retailersusecolorasapowerfulmerchandisingtool.Lightisusedtogenerateastore s imageandpricerangebyusingitswarmthandcoolness(chromaticity),itscolorquality(color renderingindex),itsintensity(illuminanceandluminance)anditsdistribution(iesna MerchandisingLightingCommittee,2001). 33

50 RetailSpaceLighting Sincedifferentareasinthestorecarryoutuniquefunctions,lightingalsorequiresspecial conditionsandattention.illuminatingengineeringsocietyofnorthamericabreaksretailspace intofourcategories:(a)displaywindow,(b)ancillaryspaces,(c)exteriorspacesand(d)sales areas(iesmerchandisinglightingcommittee,1986;iesnamerchandisinglighting Committee,2001;Rea,2000).Eachcategoryaimstofulfillthethreegoalsforretaillighting. DisplayWindows Forthedisplaywindowarea,thegoalistobeapowerfulattractor,providingthelink betweenpotentialcustomerspassingbyandthemerchandisewithinstores.asthesourceof lighting,naturaldaylightbringsawarenessoftheproducttothecustomer.atnight,theretailer shouldmakesurethatartificiallightingwouldhaveasimilarqualitytonaturaldaylight. AncillarySpaces Ancillaryspacesincludefittinganddressingrooms,alterations,workrooms,wrapping andpackingareas,stockrooms,restrooms,lounges,lockerroomsandoffices.forattracting customers,lightingindressingandfittingroomsisvitalbecausetheyareoneofthemostcritical salesareas(rea,2000).thefinalevaluationofthemerchandiseandthedecisiontobuyisoften madehere(bell&ternus,2006;iesnamerchandisinglightingcommittee,2001). Consequently,lightinginthisspacemustensuretheappropriateverticalluminance,goodcolor rendering,andtheeliminationofharshshadows(iesnamerchandisinglightingcommittee, 2001;Rea,2000).Theretailermustmakecertainthattheproducts colorappearanceisthesame aswhatthedesignersplanned.theiesnahandbook(rea,2000)recommendedthefollowing: Lightingsolutionsshouldprovideacombinationofdiffuseanddirectionallightto accentuate facial features and fabric texture without deep shadows Vertical illumination should extend far enough down to enable the customer to easily evaluatefull8lengthgarments.backgroundfinishesshouldbelightcolored,matte, andsimpleindesigntoavoidcolordistortionordistractionfromthemerchandise. Lighting for basic dressing rooms is usually comprised of overhead fluorescent lamp luminaries strategically placed to provide vertical illumination when viewingone sreflectioninthemirror Upscaleanddesignerfittingroomsand 34

51 dressingareasuseamixofincandescentandflorescentlampluminaries,aswell asluminariesfordecorativeandmoodlighting.warm(approximately3000k), high8color8renderingfluorescentlampsarewellsuitedtomirrorlighting.halogen incandescent is also excellent, provided the application results in a diffuse and well8distributedpatternoflight (p.1783) Forfittinganddressingrooms,theIESNAMerchandisingLightingCommittee (2001)recommendedtheilluminationbeplacedinfrontofthemirror(notatthemirror) tolightthecustomer.tominimizeshadowsandexhibitgreatcolorquality,the illuminationshouldbediffused.highcolorrenderingrare8earthphosphorfluorescent lamps,andhalogenareexcellentlampchoices(iesnamerchandisinglighting Committee,2001).Theexcessheatmakesincandescentlightsnotappropriateinasmall fittingroom. Inaddition,theIESNAMerchandisingLightingCommittee(2001)notedthata properlightangleforthemirrorlightisextremelysignificant.thecorrectceiling illuminationshouldbepositionedonthemirrorwallorlocatedabovethemirror.the IlluminatingEngineeringSocietyofNorthAmericaMerchandisingLightingCommittee (2001)alsorecommendedthatdownlights(i.e.PAR8type)overthemirrorshouldbe avoidedbecausetheycancreateshadows,whichinturnresultinanunflatteringviewfor customers.however,ifdownlightsareunavoidable,theiesnamerchandisinglighting Committee(2001)advisedusingwidedistributionAlampincandescentandcompact fluorescenttypes. ExteriorSpaces Entrancelightingshouldbeemphasizedtopromotesalestransactionsbybeing aestheticallypleasing,complementingthearchitecture,addressingmerchandisedisplays andgeneratingenoughvisuallightforsafepassageandasenseofsecurity.moreover, thestoreentranceshouldbeonalevelthatallowscustomerstoadaptvisuallyandmakea safetransitionbetweeninteriorandexteriorareas. 35

52 SalesAreas Lightinginthesalesareasintendstoinitiateandcompletesalestransactions.Therearea numberofaspectsthatneedtobeaddressedindesigningthelightingintheseareas,suchastypes andcharacteristicsofmerchandiseanddisplaymethod. Clothingdisplayareasareconsideredsignificantforsalesareassincepatronsfirst encounterapparelproductshere.therefore,theilluminantsengineeringsocietyofnorth Americahandbookcategorizedthreetypesoflightingusedinclothingdisplayareas:perimeter lighting,accentlighting,andfeaturelighting(rea,2000).however,theiesnamerchandising LightingCommittee(2001)classifiedfivetypesoflightingusedintheretailenvironment:(a) ambientlighting;(b)perimeterlighting;(c)featurelightingincludingracklighting,shelfand gondolalighting,counterlighting,mirrorlighting,showcaselighting,wall8caselighting,and modelinglighting;(d)accentlighting;and(e)decorativelighting. Ambientlighting.Itprovidesageneraldiffuselayerofuniformilluminance throughoutthestore.threedifferenttypesofambientlightingarethegeneralpattern system,thespecificpattern,andtheflexiblepatternsystem(iesnamerchandising LightingCommittee,2001;Rea,2000).Thegeneralpatternsystemprovidesgeneral lightingthroughoutthesalesareawithandwithoutdisplaylightingandwithoutregard formerchandisingareas.thespecificpatternisnonuniformlightingbecausethelighting layoutdependsonthetotalareaofthemerchandisedisplay.theflexiblepatternsystem isapatterncontinuousorindividualthatisnon8permanentlyinstalled.therefore,the lightcanbetailoredtothemerchandisingdisplays.theilluminancelevelofambient lightcanrangefromalow150to300lux(15to30fc)to750to1,000lux(75to100fc) dependingonthetypeofstore(iesnamerchandisinglightingcommittee,2001). Chromaticityandcolorrenderingqualityaredependantonthetargetmarketandstore concept.commonly,threebasiccategoriesfortheretailindustryarelow8end(mass merchandising),middle(departmentstore),andhigh8end(exclusive)(table7). 36

53 Table7 TheIlluminanceLevelsofIlluminantsforAmbientLightinginThreeBasicRetailStores Category Low8end Usuallyhasonlyambientlightingwith symmetricallylocatedilluminants. Middle Usuallyinvolvesgenerallighting systemwithaccentlightingforspecialty areas. High8end Usuallyemployscombinationof decorative,accentandambientlightings. Source:IESNAMerchandisingCommittee(2001). Illumianncelevels(Lux) 750to1,000lux(75to 100fc) 400to600lux(40to60 fc) 150to300lux(15to30 fc) Perimeterlighting.Ithelpscreatepleasantness,increasesbrightnessperception, improvesvisibilityofthewalldisplays,andmakesaspacefeelbigger.inotherwords, perimeterlightingdefinesmerchandisingspaces. Featurelighting.Itisusedwhenspecialattentionisneeded.Althoughthereare manycategoriesoffeaturelighting,onlyracklightingandshelfandgondolalightingwill bediscussedinthisresearch.racklighting,shelfandgondolalightingattractscustomers. Inaddition,theyaidcustomersinevaluationofthemerchandise.Illuminating EngineeringSocietyofNorthAmericastatesthatracklightingcanhelpfullyilluminate theclothingproductandrevealbothcolorandtexture(rea,2000),asdotheshelfand gondolalighting(iesnamerchandisinglightingcommittee,2001).theiesna MerchandisingLightingCommittee(2001)notedthattheappearanceofthemerchandise shouldbethesameattherackandinthefittingroom.theilluminancelevelonthe clothingshouldbegreaterthentheilluminanceoftheambientlightingbetweenracksor intheaisles.theilluminantforshelfandgondolalightingshouldbeinharmonywiththe ambientlightingaroundtheareas. Accentlighting.Itemphasizestheshape,texture,finish,andcoloroftheproduct relativetoitssurroundings.accentlightingprovidescontrastthatambientlighting cannotproduce.theiesnamerchandisinglightingcommittee(2001)statesthatpoint 37

54 sourcesareidealforaccentlightingsincetheycanbecontrolledanddirected.thetype andimageofthestoredirectlyrelatestotheamountofaccentlighting.additionally,the levelofambientlightingdeterminestheamountandintensityofaccentlighting.since thehumaneyewilladapttotheaverageilluminanceofthestore,largedifferencesin illuminancelevelscanreducetheabilitytoseedetail.withhighambientilluminance, additionalaccentilluminanceislessneededandviceversa. Forvisualmerchandisinganddisplayarenas,Pegler(1998&2006)statedthat, besideswindowlighting,twotypesofstorelightingareprimaryorgenerallighting,and secondaryoraccentlighting.bellandternus(2006)notedthat,inastoreenvironment, thelightingsystemsperformthreefunctions:ambient,accentandtasklighting.primary, ambientorgenerallightingilluminatesthefloororarea(pegler,1998;pegler,2006). Theprimarylightisanoverheadfixture.Ambientorprimarylightingprovidesgeneral, overalllightingthatdeterminescolorrendition(bell&ternus,2006).theambientor primarylightingshouldprovideadequatelightforcustomerstocompareormatchthe garments.bellandternus(2006)reported ifyou vehadtoaskasalespersontotake twogarmentsoutofthestoreintodaylighttocompareormatchcolor,youwereshopping inastoreenvironmentthatdidn tprovideadequatelighting (p.214).secondaryor accentlightingissupplementallightingeithercreatingorproducingsparkle,punch, shimmer,shadoworspecialfocalpointsorhighlightsinthesellingareaswheregeneral orprimarylightingexists(bell&ternus,2006;pegler,1998;pegler,2006).secondary oraccentlightingaddsimpression,atmosphereelements,ormoodinthestore.the secondaryoraccentlightingalsomakesmerchandisestandoutfromitsenvironment sincethesecondaryoraccentlightingmakesthecolorofthemerchandiseappearsharper andmorebrilliantandbringsoutthetexturedetails(pegler,1998;pegler,2006).task lightingisusuallyusedinworkareasincludingalterationrooms,fittingrooms, stockrooms,restrooms,officesandcheckouts(bell&ternus,2006). LampsUsedinRetailIndustry Lampsarecategorizedbylightingengineers/designersandvisualmerchandise anddisplayexperts.thecategoriesoflampsare(a)fluorescent,(b)incandescent,(c) halogen,(d)high8intensitydischarge(hid)lightingand(e)light8emittingdiode(led). 38

55 TheIESNAMerchandisingLightingCommittee(2001)comparedthecharacteristicsof lampsusedinretailmarketing. Fluorescent.Asmentionedearlier,GordonandNuckolls(1995)foundthat fluorescentlampsproduceadiscontinuousspectrum:peaksofenergyatspecific wavelengths.becauseofvariationsincompositionofthephosphorsthatcoattheinside ofthefluorescentlamp,thecolorofemittedlightisdifferent(gordon&nuckolls,1995). Fluorescentlampsareavailableinvariousdegreesofwarmthandcoolness(Gordon& Nuckolls,1995;Pegler,1998;Pegler,2006).Someofthemanytypesoffluorescent lampsusedintheretailindustryarecoolwhitefluorescentorcwf(hoover,1997), compactfluorescentlampsorcfl,andt8andt5(bauer,2006).asalightingdesigner, Bauer(2006)explainedthatbecauseoftheimprovementoflamprefinementsandgreater ballastoptions,t8andt5fluorescentlampsprovidelongerlamplifeaswellasbetter efficiencyandperformance.originallyt8lampshadlamplifeofabout20,000hoursbut theimprovedt8hasincreasedthehoursto24,000830,000(bauer,2006).belland Ternus(2006)claimedthatfluorescentlampsarethebestambientorprimarylighting sincetheyaretheleastenergyconsuming.whiletheiesnamerchandisinglighting Committee(2001)proposedthatT8andT12(linearfluorescent)lampsarethemost commonlampsforambientorprimarylightingandwallwashing.comparedto incandescentlamps,fluorescentlampsconsumeonlyone8fifthoftheenergyandproduce onlyone8fifthoftheheatbutprovidethesameamountoflight(bell&ternus,2006; Pegler,1998).Moreover,fluorescentlampshavealongerlifespanandahighdegreeof lumens,whichis ameasureoflightcomingfromanysourcecomparedtotheamountof lightproducedbyaburningcandle(p.214) perwatt(bell&ternus,2006).however, althoughfluorescentlampsareeasierforcontractorstoinstallandforretailersto maintain,theyarenotsuitableformanycategoriesofmerchandisinganddisplay(bell& Ternus,2006;Pegler,1998).Inretailstores,fluorescentlampsareusuallycombined withincandescentlamps(bell,&ternus,2006;hinksetal.,2000;hinksetal.,2001; Pegler,1998;Pegler,2006Thiry,2004). Incandescent.Incandescentlampsemitsmoothcurveenergyinasmallamountofdeep blueradiationclosesttotheultravioletrange,andthenincreaseenergyintothedeepredportion ofthespectrum(gordon&nuckolls,1995).usually,incandescentlampsprovidethewarm 39

56 colorsofredandyellowandhaveagoodcolorrendering(bell&ternus,2006;gordon& Nuckolls,1995;Pegler,1998).TheIESNAMerchandisingLightingCommittee(2001)added thattheadvantagesofincandescentlightingarelowinitialcost,pleasantcolor,excellentcolor rendering(cri=100),opticalcontrolcapabilities,versatility/flexibilityandsimpledimming. Incandescentlampsareconsideredtobethebestlightingsystemforsecondaryandtasklighting becausetheyprovideadefinedareaoflight(bell&ternus,2006).overalllightingisbest providedbyafluorescentlightingsystem.twotypesofincandescentlightingusedtodefinean areaarefloodandspotlamps.normally,floodlampsorfloodlightsareforawideareabecause theyhaveawiderbeamspreadfromthefrostedglassenvelopesorenclosures,andspotlampsor spotlightscoverarangefrom1inchto6feet.eventhoughfluorescentlampsaregoodfor lightinganaisle,washingawallorindicatingthetypeofmerchandise,incandescentlampsmake thesale(pegler,1998).thedisadvantagesofincandescentlampsarethattheyaremore expensivetoinstallandmaintain,haveashorterlamplife,aremoreenergyconsumingandgive offmoreheat.however,bauer(2006)arguedthatapackageoft5fluorescentfixturesisbetter forcaseworkandunder8shelfilluminationsinceitissmall.althoughthet5systemistwoto threetimesmoreexpensivethant8fluorescent,thet5sarestillwidelyusedforsomeretail applicationsduetotheirsizeandimprovedperformance.bauer(2006)foundthatthecompact fluorescentlamps(cfl)areusedasanalternativetoincandescentfordecorativeluminaries sincetheyarenowavailableinrectangularandsquareshapes;however,thedrawbackistheir efficiencyrelativetohalogenlamps. Halogen.Itisanothertypeofincandescentlightingcommonlyusedforaccentandtask lighting(bell&ternus,2006).halogenlightingprovidescolorrenderingclosetodaylight. Benefitsofhalogenlampsaretheirlongerlamplifeandthehighestlumenefficiencyofany system.theyaremoreefficientthanstandardincandescentlampsby10to20percentanda switchcancontrollightlevels.theiesnamerchandisinglightingcommittee(2001)purposed thatforretailapplicationsthecommonbulbshapesarear(aluminizedreflector,par(parabolic aluminizedreflector),andmr(multifacetedreflector).bauer(2006)addedthatthemostrecent versionofhalogenirparlampswhichisavailablefordisplayandaccentlightingoffers10 percentmoreefficiencywithanequivalentoutputoflightcomparedtothepriordesign. Moreover,withinthenexttwoyears,theIRhalogenlampswillhaveimprovedperformanceto thepointof20to25percentormore(bauer,2006).disadvantagesofhalogenlightingare 40

57 intenseheatthatmayharmmerchandiseifplacedtoocloseandthecomplicationsoflamp changing. Foraccentandfocallighting,halogenlampscalledMR16orMR11aremostpopularin retaillighting.themr16andmr11offerasharpbrightlightandproduceacolorbalancethat comesclosetosunlight(pegler,1998).thelow8voltagelampsareenergyefficient,inexpensive, compact,cooler,donotharmmerchandiseandareeasytoclean.moreover,colorsappeartruer underthesetwolamps(pegler,1998). Highintensitydischarge(HID).TheHIDisveryenergyefficient.AccordingtoPegler (1998),theHIDwillbecomepopularforbothgeneraluseandoverallstorelightinginretail stores.comparedtofluorescent,thehidsarerelativelysmallerinsizebutalsoareavailableas longfixtures,soinsomecasescouldreplacethefluorescents.thehidshavethesameproperty ofprovidingshadowsandhighlightsasincandescents.acoupletypesofhidareavailablefor retailstoresincludingthemercury8typehid,themetalhalideandthesodiumvapor.initially, thehidshadsomeproblems.themercurytypemayappeartoogreen,themetalhalidemaybe tooblueandthesodiumvapormaylookyellow(pegler,1998).however,luminarie manufacturershavedevelopednewimprovedhidsthatofferwarmerandmoreflatteringtypes oflight.forexample,generalelectrichaslaunchedanewmetalhalidetypelampcalledmulti8 VaporIIthatproducesalightsimilartoastandardcoolwhitefluorescent(Pegler,1998).Bauer (2006)statedthatnewdevelopmentsinceramicmetalhalide(CMH)arenowavailableinlow wattage(aslowas20watts)withalumenpackageequalto75wattsofhalogenlamps. Moreover,anewelectronicCMHballastincreasescolorstability,whichmeanslesscolorshift, andlumenmaintenance.bauer(2006)notedthatcmhaccentlightingnowhasaprimetime statusinretaillightingsinceusingitisalmostmandatoryforlightingadesignerwhodesiresboth highilluminationlevelsandmaximumaccentlightratios.thedrawbackofusingcmhisthe cost.cmhlamppricescanbesixtotentimeshigherthanthatofahalogenlamp(bauer,2006). Lightemittingdiode(LED).Forprovidingtheaterthemeeffects,coloredwalls,graphics andsigns,ledshavebeenutilizedformanyyearsinretaillighting;however,lightingdesigners haverecentlybeguntousethemincaseworkandunder8shelfapplications(bauer,2006).since 2005,LEDshavebeenimprovinginwhitelightquality,lumenoutputandlamplife.Forthese reasons,ledsarenowapplicableforthejobsthatneon/coldcathodeandsmall8lamp 41

58 incandescentsusedtofill.however,ledshavethesameproblemascmhintheirhighcost. Therefore,onlycuttingedgestoresandthosewhohavehealthyconstructionbudgetsuseLEDs intheirprojects. ColorandLightingUsinginTextilesandRetailIndustries Inthetextileandretailindustriesthereisanincreasedawarenessandconcernregarding obtainingaccuratecolor.thisresultsinacademic,expert,andprofessionaleffortsinboththe textileandretailindustriestowardsconductingresearchonlightingandcolor.however,very littleinformationisavailableintheliterature.hoover(1997)saidthatretailersarenolonger usingonlyonelightsource,coolwhitefluorescent(cwf),buthavemovedtoamulti8source function.moreover,hooverstatedthateventhethreelargebulbmanufacturerssuggestclothing retailersshouldlighttheirstoreat kwhichincludesfluorescents,compact fluorescents,halogen,parfloodsandhalides(1997).theilluminatingengineeringsociety RecommendedPracticesforLightingMerchandisingAreas(1986)statedthat merchandise shouldbedisplayedunderthesamelightingsystem,withthesameapparentluminanceasduring itsultimateuse (p.46).azoulay(2005)notedthattargetcompanyhasanawarenessofthe lightingissue.thatiswhytheytrytostandardizetheirstorewithonetypeofthelightingand alsorequiretheirdyerstosubmittheirlabdip,asampleofdyedfabric,forapprovaland standardizetheircolorcommunicationsoftwarewiththeirvendors.theprobleminretail lightingisthatthespdsofafluorescentlightsource,whichisthemostenergyefficient,differ greatlyfromthoseofdaylight(asoulay,2005).heschong,wrightandokura(2002)concluded thatanincreaseinsalesassociatedwithadaylitstoremightbepossiblybecausedaylighthelps improvevisionduetothehigherilluminationlevelandbettercolorrendition.hinksetal.(2001) foundthatamedium8sizedretailstore(approximately5000ft 2 )withlimitedexternalwindows hasvariablelighting.usingthestandardilluminantinformationprovidedbythestoredoesnot producetheaccurateandadequateinformationneededtopredicttheeffectoflightincolor difference,metamerism,andcolorconstancybecauseofthevariabilityonstorelighting(hinket al.,2001).accordingtohinksetal.(2000),thelightinginretailstoresdiffersfromthestandard illuminants.hinksandhiscolleagues(2000)determinedthatthefollowingconditionsmay causevariabilityinlighting:(a)lampsincorrectlyinstalled;(b)differenttypesoflampsused togetherinthesameregionofspace;(c)lampemissionvariability,(d)lightfromentrance/exit areasaswellasexteriorwindows;and(e)stronglycoloredsurfaces. 42

59 Metamerism Researchers(Berns,2000;Collishawetal.,2004;Hinksetal.,2000)statethatan illuminantmetamerismoccurswhenapairofobjectsdiffersincolorwhenviewedunder differentilluminants. Tominimizethemetamerism,usingtheindicesofmetamerism,whichis thecolor differencebetweenabatchandthestandardforthetestcondition (Berns,2000,p.127),is recommended.berns(2000)suggestedthatthemostcommonindicesarebasedoncolorimetric coordinates.theprocessstartswithdefiningareferenceorstandardconditionwithametameric matchandthenusingatestconditiontotestapairofspecimensformetamerism.forexample, theuserspecifiesareferenceconditionascieilluminantd65withthe196410degreestandard observerbutactuallyusesilluminantaandthe196410degreestandardobserverasatest condition.sinceilluminantmetamerismhappenswhenviewingthesamepairofspecimens underdifferentilluminants,ifapairofmetamericsamplesmatchedinbothilluminants(d65and A),itwasassumedthatmetamerismwouldnotbeaproblemundervariousrealsources.Inthis case,thecieilluminantisaprimaryilluminantwhiletheilluminantaisasecondaryortertiary illuminant.berns(2000)advocatedaneedtoevaluatethemetamerismforilluminated65,a,f2 andf11,andthenrankthembyprimary,secondary,tertiaryandquaternaryinordertousea metamericindextoaverageweightforeachcolordifference. Hinksetal.(2000)statedthattopredictandcomparecolordifferencebetweenastandard andbatchforseveralilluminantsisuniversallypracticedforestimatingthedegreeof metamerism.usingametamerismindex(mi)canapproximatethedegreeofmetamerismfora metamericpairundertwoilluminants.thecomparisonsbetweentheprimaryandsecondary illuminantsaresetupforcolordifferencechangesorchangeofilluminant.furthermore,hinks etal.notedthatcarefullyselectingtheprimaryandsecondaryilluminantswillhelpminimizethe momentumriskintheshiftingofcolordifference(2000).hinksetal.(2000)advisedretail storestoevaluatethelightingconditionsunderwhichobjectsarenormallyusedtodeterminethe arealightingvariability. ColorInconstancy AccordingtoHinksetal.(2000),colorinconstancyorflaremeans thechangein perceivedcolorofanobjectuponchangingtheilluminant(p.16). Berns(2000)alsogavea 43

60 verypracticalandeasywaytounderstandthemeaningofcolorinconstancyas thecolor differencebetweenthecolorimetriccoordinatesunderthereferenceandtestilluminants (p. 130).Additionally,Collishawetal.(2004)definedcolorinconstancyassimply thechangeof shadeofasinglesample (p.16).colorconstancyisveryimportantinthetextileindustryand veryusefulformanyapplicationssuchasinsafetycolors,color8ordersystems,andengineering becausecolorinconstancymightcausesomeseriouseffects.forexample,ifavestofasafety colorforaconstructionworkervariesincolor,adrivermaynotseeawearerandanaccident mayresult.althoughitisimpossibletoobtainabsolutecolorconstancyindyedtextilestandards, itispossibletominimizethecolorinconstancyforinsensitiveneutralandternaryshades (Collishawetal.,2004).Whenreproducingcolorinplasticortextileproducts,thecolorrecipe thathastheleastcolorinconstancyisthebestrecipe.usingthecolorinconstancyindex(cii)as anapproachtoestimatethecolorinconstancyisimportantbecauseitispossiblethatapairof samplesmightappearlowinmetamerism,butretaininconstancyincolor.berns(2000)and Kadolph(1998)mentionedthatthechangeinhueismorenoticeablethanthechangeinvalue andchroma.inotherwords,comparedtohuechanges,valueandchromachangeshaveonly one8halfoftheimpactvalue.manyexpertsemphasizethedifferencebetweenmetamerismand colorinconstancy.eventhoughbothofthemarerelatedtochangesincolorswhenviewed underdifferentilluminants,thecolorinconstancyappliesonlytoasinglesamplewhile metamerismisusedwithatleastapairofsamples(berns,2000;collishawetal.,2004;hinkset al.,2000). ColorMeasurement Instrumentalandvisualarethetwotypicalwaystoassessqualityofcolor.Visualcolor measurementisfundamentalformeasuringcolorsincethegoalofinstrumentalcolor measurementis toestimatewhatanobserversees,thecolorappearance (Berns,2000,p.76). VisualColorMeasurement AsreportedbyBerns(2000),althoughinthelastdecadevisualcolormeasurementwas consideredimportanttocolortechnology,itismoredifficulttofindvisualinformationregarding comparingcolorsthanbyinstrumentalcolormeasurement.berns(2000)andkadolph(1998) haveprovidedpossibleexplanationsforthelackofvisualinformation.instrumental 44

61 measurementsarestate8of8theart.visualmeasurementsaresubordinatetoinstrumentalbecause theresultsofvisualmeasurementsarenotasaccurateasinstrumental. StandardizedIlluminatingandViewingConditions Definingtheilluminatingconditionsisthefirststepinvisualcolormeasurement. AccordingtoBerns(2000),theconditionsinalightboothshouldbestableovertime.When duplicatinglightingconditions,thebooth sspectralpowerdistribution(spd)andlevelof illuminationshouldbepreciselythesameastheconditioninwhichthesampleisbeingspecified. Whenthespecificationrequiresartificialillumination,thisisreasonableandachievablebecause toduplicatetheartificiallightsourceiseasyandpossible.comparedtoartificialillumination, thespecificationsthatrequirenaturaldaylightareproblematicsinceallpracticallightsourcesfor visualcolormeasurementresemblenaturaldaylightpoorlyinbothspdandlevelofillumination (Berns,2000;Harold,2005a).Moreover,definingwhatnaturaldaylightmeansisdifficult. Woulditmeanlightatnoonorinthemorning?Woulditbelightduringfallorsummer?Even thoughcieoffersmanystandarddaylightilluminants(e.g.d50,d65andd75),thereisno equivalentciestandardsourcethatcouldbeusedinthelightbooth.berns(2000) recommendedredefiningstandardizedlighting.thebestwaytore8standardizelightinginthe lightboothistousetheclosestsimulationtotheintendedreal8worldlightingconditions. Definingasurroundingisthesecondstepforvisualcolormeasurement.Bernsgavethe definitionforsurroundingas thebooth sinteriorwalls (2000,p.79).Thesurroundingshould bematteandneutral.thesimulatedlightingenvironmentwillidentifythelightnessofthe surrounding.normally,theilluminationisnotcompletelydirectionalbecausetheextended sourcesanddiffusersareoftenplacedbelowthesource.thesecondaryreflectionsfromthe wallsontotheflooroftheboothincreasewhenthewallsincreaseinlightness.theeffectof increasingthediffusecharacteroftheboothissimilartoovercastskyconditions(berns,2000). Ifthematerialisnothighlyglossy,itisbesttoleavethesurroundingcharacteristicsunchanged. Inthecaseofevaluatinghighlyglossymaterial,thebackoftheboothshouldbeblackened. Berns(2000)recommendedusingblackvelvetbecauseitwillhelptoeliminatethespecular reflectionsdefinedasseeinganimageonthebackofthebooth. Bernsreferredtobackgroundas thesurfaceuponwhichsamplesareplaced (2000,p. 79).Toestimatecolorappearance,thebackgroundshouldbematteandwithamiddlelightness 45

62 (L*=50).AccordingtotheAmericanSocietyofTestingandMaterials(ASTM)Designation 1729,toenhancesmallcolordifferences,whenevaluatingcolordifference,thebackgroundlight issometimesvaried(2006). MeasuringtheSPDsandilluminancesorlevelsofilluminationisthenextstepinvisual measurement.theidealilluminancesforallsourcesshouldbeatorwithin100lux(berns, 2000).However,illuminancescanvarybroadlyinapracticalsituationbyasmuchas1,000lux. Forvisualcolormeasurement,1,000luxor93footcandlesareareasonableilluminancelevel. Someimportantfeaturesneedtotakenintoconsiderationbeforeevaluatingcolorvisual measurement.theyarethesample,positionofthespecimenandtheoverheadlighting. 1.Sample Thesamplesshouldbeofaconsistentsizebecausevisualprecisioncanbeincreasedby largersizesofthesamples.onaverage,thesampleshouldbeatleasttwoinchessquare. However,ifthissizecannotbeaccomplishedandasmallersamplesizemustbeused,itis recommendedthattheobserversshouldviewthesamplefromadistancesuchthatthevisual angleisnotlessthan2 (Berns,2000)(Figure11).Incasethestandardissmallerthanthe sample,amaskshouldbeusedtoequalizetheareaofthespecimens.berns(2000)remarked thatthemaskandthebackgroundshouldhavethesamelightnessandsurfacecharacteristics. Forcolordifferencesbetweentwoormorespecimens,theidenticalpairofsamplesshouldbe separated. Figure11:Thevisualangleofsubtense. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.79.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. 46

63 2.Specimenpositioning Specimensshouldbepositionedontheflooroftheboothbecausetheilluminationwillbe centeredata908degreeangletotheplaneofthespecimens(berns,2000).moreover,the observershouldstandabout6to12inchesfromtheopeningoftheboothandataheightsuchthat theobservationangleis458degreesfromnormalor08degreetothespecimens(figure12).berns (2000)pointedoutthatitiscriticalfortheobserverstomaintainthesamedistancefromthe specimensduringvisualevaluations.forcolordifferences,thespecimensarecommonlyplaced inedgecontact.theilluminationwillbedifferentbetweenlargelydirectionallightand moderatelydiffuselightdependingontheparticularlightsource,diffuserandsurroundlightness. Figure12:Theobserverandthelightbooth. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.80.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. 3.Overheadlight Theoverheadlightshouldbeturnedoffbecauseitwillinterferewhentheobserverviews thesampleunderthelightbooth.furthermore,inthelightbooth,thereshouldbeonlyone specimenatatimeforvisualevaluationbecausethespectralpropertiesofthelightingaresubject tochangewhichisappreciableiftheboothislitteredwithspecimens(berns,2000). 47

64 PurposeforVisualAssessment Threepurposesforvisualmeasurementaremeasuringcolor(a)appearance,(b)equality and(c)matching. Measuringcolorappearance.Colorappearanceisanaspectofvisualinspectionofcolor. Therefore,visualappearancemeasurementisaqualitativeevaluation.Theprocedureof measuringcolorappearancestartswithpositioningasinglespecimeninthelightboothwithonly oneofthelightsturnedon.beforeobservingthecolor,aviewerneedstoadapthis/hervisual systembylookingaroundthewallsofthelightboothfor60seconds.humaneyestake60 secondsforlightadaptation(berns,2000).theobserverwillassignacolornotationbasedona color8ordersystemsuchasthemunsellcolorsystem.berns(2000)suggestedthattheobserver shouldevaluatethecolorwithoutstaringatthesampleforlongperiodsoftimeinordertoavoid localadaptationtothecolorofthespecimen. Sometimestheobserverhastoevaluatecolorappearancewithmorethanonelightsource. Consequently,whenswitchingthelightsource,theviewerwillresthis/hereyesbyroaming aroundtheboothwallsforanother60seconds.then,he/shecanevaluatethespecimenand nameanothercolornotation.theobserverwillrepeattheprocessforeachsourceofinterest. Theprocedurefordeterminingthecolorinconstancyofthestandardissimilartothe colorappearancemethod,buttheobserverwillexamineforsignificanthuevariationina specimenunderchangesinlighting(figure13).berns(2000)statedthatastandardwithpoor colorconstancyshouldnotbeusedincolormeasurement. 48

65 Figure13:Colorinconstancy:underdifferentlightsources. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.129.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. Measuringcolorequality.Therearetwodifferentmethodsforassessingcolorequality: sampleandsinglestandardandsampleandmultiplestandards. 1.Sampleandsinglestandard Onesampleandasinglestandardareevaluatedintheboothatthesametimebyan observerusingastandardizedlightsource(figure14).colorequalityisthedeterminationof whetherthetwosamplesareorarenotidenticalwithrespecttocolor.judgingthecolorequality involvesthevisualinspectionoftwosamples,side8by8side,understandardizedlighting conditions.berns(2000)recommendedthatasinglelightsourceisnotenoughforappropriate examinationinmostcases;thus,multiplestandardizedsourcesshouldbeagreedupon. 49

66 Figure14:Sampleandsinglestandard. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.81.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. 2.Sampleandmultiplestandards Whentheresultsofasinglestandardforevaluatingcolorequalitybetweenthestandard andsampledonotmatch,berns(2000)foundthisaconsequenceofthesinglestandardonly involvingonepointinathree8dimensionalworldofcolor.inotherwords,theproblemofthe singlestandardisthattheobservercanonlypointoutthatthesampleandsinglestandardmatch ordonotbutcannotgivefurtherinformationsuchasestimatingthenatureofthedifference betweenthesampleandstandard,orhowgreatthedifferenceisinrespecttoequalityorhow largethedifferenceisduetolimitationsoftheeye. Thesolutionforthehumaneyelimitationistoprovidemorethanonestandardwith whichtomakecomparisons.withmultiplestandardsfortheobservertoratethedifferences,the visualassessmentcanchangefromqualitativetoquantitativeanalysis.asecondstandardcanbe placedadistanceawayfromthefirststandardinagivendirectionincolorspace.theobserver willbeaskedtoevaluatewhetherthesampleisclosertoorfatherawayfromtheprimaryor targetstandardthanthesecondorlimitedstandard(figures15and16). 50

67 Figure15:Sampleandmultiplestandards. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.81.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. Figure16:Visualtolerancechartsaresometimesusedinevaluatingcolorquality. From BillmeyerandSaltzman sprinciplesofcolortechnology, bys.r.berns,2000,newyork:awiley8 Intersciencepublication,p.82.Copyright2000byJohnWiley&Sons,Inc.Reprintedwithpermissionofthe publisher. Measuringcolormatching.Manyindustries(i.e.,textile,paint,orplastic)conductcolor matchingintheirmanufacturingprocess,qualityassurance,orproductdevelopment;however, differentfieldsmayhavealternativetechniquesorprocedures(generalelectriccompany,1994). Therearetwomethodsforassessingcolor(instrumentandvisualevaluations)andtheinstrument oneismorepreferableandaccurate;however,forcolormatching,visualassessmentisbetter becausetheeyeisthebestnulldetection.sinclair(1997)recommendedseveralfactorsforcolor matchingspecification:(a)theintensityofthelightsource;(b)theangleofilluminationand 51