3 LIGHTINGQUALITY

41

Chapter3:Lightingquality

Topicscovered

3 Lightingquality................................. ........................................................................................ 433.1 Lightingpracticesandqualityinthepast:his toricalaspects .................................... ..... 433.2 Defininglightingquality ...................... .......................................................................... 433.3 Visualaspects................................. ................................................................................ 45

3.3.1 Visualperformance........................... ................................................................ 453.3.2 Visualcomfort ............................... ................................................................... 45

Colorcharacteristics.............................. ........................................................... 46Uniformityoflighting............................. ......................................................... 47Glare................................................................................................................. 47Veilingreflections................................ ............................................................ 48Shadows ........................................................................................................... 48Flicker .............................................................................................................. 48

3.4 Psychologicalaspectsoflight ................. ....................................................................... 483.5 Nonvisualaspectsoflight .................... ........................................................................ 493.6 Lightingandproductivity...................... ......................................................................... 503.7 Effectsofelectromagneticfieldsonhealthand opticalradiationsafetyrequirements.. 513.8 Conclusions:opportunitiesandbarriers........ ................................................................. 52

3.8.1 Opportunities................................ ..................................................................... 523.8.2 Risks........................................ .......................................................................... 53

References ................................................................................................................................ 54

3 LIGHTINGQUALITY

42

3 LIGHTINGQUALITY

43

3 Lightingquality3.1 Lightingpracticesandqualityinthepast:histori calaspectsThe use of electrical lighting, even in the industr ialisedworld, is quite recent. Electrical lightingbegan to spread widely with the development and use of the incandescent lamps. The use ofincandescentlampreachedalargescaleatthebegi nningofthe20 th century.

Forthousandsofyears,peoplereliedmainlyonday lightandfire(bonfire,torches,candlesandoil).The fundamentalsof lightingat that timewere rela ted to thequantityof light thatwas toprovidelightforpeopletoseeandcopeinthevisualenvi ronmentalsoduringthedarkhours.

Powerful lamps such as fluorescent lamps came to th e market in the 1950s with the followingintroduction of high-intensity discharge lamps. The development of powerful bright light sourceslead to considerations of avoiding glare (using lig ht diffusers, later light louvres). Moving fromincandescent light sources todischarge light sourc es raised the issueof color renderingandcolortemperature. Today, LEDs are entering the lighting market and as new light sources they enablenew approaches to lighting design and practice. LED s introduce new possibilities for tuning thecoloroflightandcomparedtoconventionallights ourcestheyaresmallinsizegivingalsofreedomforluminairedesign.

Today, the variety and number of lighting equipment manufacturers has grown, but thefundamentalsof lighting remains the same.Thesear e to supply enough lightwithproper lightingdistribution in space, with good spectral qualities and little or no glare, at reasonable costs. Thedevelopmentoflightsourcesandlightingequipment providesbothopportunitiesandchallengesforthe lightingdesigners inproviding lighting that i snotonlyadequate in termsofquantity,butalsomeetsthelightingqualitydemands.

Figure3-1. LEDsareusedtodaytoprovidelightinginversati le applications;rangingfromlightingofofficebuil dingstolightingofhomesindevelopingcountries.

3.2 DefininglightingqualityWhatdoeslightingqualitymean?Thereisnocomple teanswertothequestion.Lightingqualityisdepends on several factors. It depends largely on p eoples expectations and past experiences ofelectriclighting.Thosewhoexperienceelementary electriclightingforthefirsttime,forexample,in remote villages in developing countries, have di fferent expectations and attitudes towardslightingfromofficeworkersinindustrializedcoun tries.Therearealsolargeindividualdifferencesinwhatisconsideredcomfortablelighting,aswell asculturaldifferencesbetweendifferentregions.

3 LIGHTINGQUALITY

44

Visualcomfortisalsohighlydependentontheappl ication,forexamplelightingthatisconsideredcomfortable in an entertainment setting may be disl iked and regarded as uncomfortable in aworkingspace(Boyce2003).

Lightingqualityismuchmorethanjustprovidinga nappropriatequantityoflight.Otherfactorsthatare potential contributors to lighting quality incl ude e.g. illuminance uniformity, luminancedistributions,lightcolorcharacteristicsandglar e(VeitchandNewsham1998).

There are many physical and physiological factors t hat can influence the perception of lightingquality. Lighting quality can not be expressed simp ly in terms of photometricmeasures nor cantherebeasingleuniversallyapplicablerecipefor goodqualitylighting(Boyce2003,Veitch2001).Lightqualitycanbe judgedaccording to the level ofvisualcomfortandperformancerequiredforouractivities.Thisisthevisualaspect.Itcana lsobeassessedonthebasisofthepleasantnessof thevisual environment and its adaptation to the type o f room and activity. This is the psychologicalaspect.Therearealsolongtermeffectsoflighto nourhealth,whicharerelatedeithertothestrai nonoureyescausedbypoorlighting(again,thisis avisualaspect),ortononvisualaspectsrelatedtotheeffectsoflightonthehumancircadiansyst em(Brainard etal. 2001,Cajochen etal. 2005).

A number of different approaches have been suggeste d to define lighting quality (Bear and Bell1992,LoeandRowlands1996,VeitchandNewsham199 8,BoyceandCuttle1998).Thedefinitionthat seemsmost generally applicable is that lighti ng quality is given by the extent to which theinstallationmeetstheobjectivesandconstraintss etbytheclientandthedesigner(Boyce2003).Inthis way lighting quality is related to objectives like enhancing performance of relevant tasks,creatingspecificimpressions,generatingdesiredp atternofbehaviourandensuringvisualcomfort.The constraints may be set by the available financi al budgets and resources, set time-lines forcompletingtheprojectandpossiblepredeterminedp racticesanddesignapproachesthatneedtobefollowed.

Lightingquality is also a financial issuewhichca nbebest illustrated in thecaseof the luminousenvironmentofworkspaces.Anassessment inFrench offices shows thata typical yearlyelectriclighting consumption amounts for about 4 /m 2, and total yearly ownership cost of lightinginstallationsisaround8to10/m 2 (Fontoynont2008).Thishastobecomparedtothey earlycostofsalariesforthecompanies,ofabout3,500/m 2,withthehypothesisofanemployeecosting35,000/year, requiringabout10m 2 ofoffice space.Thus,average total lightingcost speremployeearebetween80to100/year.Assumingworkinghoursof 1,600hrs/year,oracostperhourof35,000/1,600hour= 21 /hour, it can be seen that the to tal cost of lighting required by an employee isequivalent to 4 to 5 hours of work per year, or 0.3 % of the yearly employee costs. This figuredemonstrates theriskofofferingpoor lightingenv ironment to theofficeemployees.Poor lightingconditionscaneasilyresultinlossesinproductiv ityoftheemployeesandtheresultingproductioncostsoftheemployercanbemuchhigherthanthea nnualownershipcostoflighting.

Thus, any attempt to develop energy efficient light ing strategy should, as the first priority,guaranteethatthequalityoftheluminousenvironm entisashighaspossible.Theresultspresentedin this guidebook demonstrate that this is achievab le, even with high savings in electricityconsumption. In thesearchforhighlyefficient lig htingschemes, it isessential to fullyunderstandthe detailed lighting specification of given enviro nments. The integration of this knowledge inlightingdesignleadstoopportunitiestodevelopw in-winscenarios,offeringcombinationofenergyperformanceandlightingquality.

3 LIGHTINGQUALITY

45

3.3 Visualaspects3.3.1 VisualperformanceOne of the major aspects of the lighting practice a nd recommendations is to provide adequatelightingforpeopletocarryouttheirvisualtasks .Visibilityisdefinedbyourabilitytodetectob jectsorsignsofgivendimensions,atgivendistancesan dwithgivencontrastswiththebackground(CIE1978). In buildings, typical applications include l ighting conditions for writing, typing, reading,communicating andviewing slides andvideos, or per formingdetailed tasks like sortingproducts.Visualperformance is definedby the speedand accu racyofperforming avisual task (CIE1987)and visual performance models are used to evaluate the interrelationships between visual taskperformance,visual targetsizeandcontrast,obser verageand luminance levels (CIE2002).Lightlevels that are optimised in terms of visual perfor mance should guarantee that the visualperformance can be carried out well above the visib ility threshold limits. Visual performance isimproved with increasing luminance. Yet, there is a plateau above which further increases inluminancedonotleadtoimprovementsinvisualper formance(ReaandOuellette1991,CIE2002).Thus increasing luminance levels above theoptimum forvisualperformancemaynotbe justifiedand can on the contrary lead to excessive use of en ergy. The visual performance aspect andconsumptionofelectricity for lightingshouldbe i nbalanceinorderto increaseenergyefficiency,notofcourse,forgettingthelightingqualityaspe cts.

Figure3-2. Relativevisualperformanceasafunctionofbackgr oundluminanceandtargetcontrast.(Halonen1993)

Ensuring adequate and appropriate light levels (qua ntity of light) is only an elementary step increatingcomfortableandgood-qualityluminousand visualenvironments.Itcanbeagreedthatbad-quality lighting does not allow people to see what they need to see and/or it can cause visualdiscomfort.On theotherhand, lighting that isade quate forvisual tasksanddoesnotcausevisualdiscomfortisnotnecessarilygood-qualitylighting .Also,dependingonthespecificapplicationandcase,bothinsufficientlightingandtoomuchlight canleadtobad-qualitylighting.

3.3.2 VisualcomfortThere are a number of lighting-related factors that may cause visual discomfort and there is nostraight-forward path to follow in creating visuall y comfortable luminous environments (Boyce2003,Veitch1998).Thecurrentindoorlightingrec ommendationsgiverangesofilluminancevaluesfor different types of rooms and activities (EN1246 4-1 2002, CIBSE 1997, IESNA 2000). In

3 LIGHTINGQUALITY

46

addition, guidelines on light distribution in a spa ce, the limitation of glare, and the light colorcharacteristicsaregiven.Attentionalsoneedsto bepaidtotheeliminationofveilingreflectionsa ndtotheformationofshadowsinthespace.Therecom mendationsandguidelinesconcernmainlytheelimination of visual discomfort, but lighting desi gner can add on that to provide visual comfort.Causes of visual discomfort can be too little light and too much light, too much variation inluminousdistribution,toouniformlighting,annoyi ngglare,veilingreflections,toostrongshadowsandflickerfromlightsources.

ColorcharacteristicsThecolorcharacteristicsof light inspacearedet erminedbythespectralpowerdistribution(SPD)of the light source and the reflectance properties of the surfaces in the room. The color of lightsourcesisusuallydescribedbytwoproperties,nam elythecorrelatedcolortemperature(CCT)andgeneral color rendering index (CRI). The color appe arance of a light source is evaluated by itscorrelatedcolortemperature(CCT).Forexample,in candescentlampswithCCTof2700Khaveayellowishcolorappearanceandtheir light isdescr ibedas warm.Certaintypeoffluorescent lampsorwhiteLEDshaveCCTofaround6000Kwithbluish appearanceandlightdescribedas cool .TheCRI of theCIEmeasures howwell a given light sour ce renders a set of test colors relative to areference source of the same correlated color tempe rature as the light source in question (CIE1995).ThegeneralCRIoftheCIEiscalculatedas theaverageofspecialCRIsforeighttestcolors.The reference light source is Planckian radiator (i ncandescent type source) for light sourceswithCCTbelow5000Kandaformofadaylightsourcefo rlightsourceswithCCTabove5000K.ThehigherthegeneralCRI,thebetteristhecolorren deringofalightsource,themaximumvaluebeing100. TheCIE generalCRI has its limitations.The shortc omings of theCRImaybecome evidentwhen applied to LED light sources as a result of th eir peaked spectra. The CIE (CIE 2007)recommends the development of a new color rendering index (or a set of new color renderingindices), which should be applicable to all types o f light sources including white LEDs. CIEtechnicalcommitteeTC1-69ColorrenderingofWhite LightSourcesiscurrentlyinvestigatingtheissue.

Figure 3-3. Light source spectrum, i.e. radiant power distribut ion over the visiblewavelengths, determines the li ghtcolor characteristics.Examples of spectra of an in candescent lamp (CCT=2690K,CRI=99), a compact f luorescentlamp(CCT=2780K,CRI=83)andawhiteLEDlamp( CCT=6010K,CRI=78).

The Kruithof effect describes the psychological eff ects of preferences for varying CCT andilluminancelevel.ItproposesthatlowCCTsarepr eferredatlowilluminances,andhighCCTsarepreferred over high illuminances (Kruithof 1941). T heKruithof effect is not, however, generallysupported in later studies (BoyceandCuttle1990, DavisandGinthner1990). It is also suggestedthat color adaptationoccurswhenpeople spendcert ain time in a space, afterwhich it is nomorepossibletocomparelampswithdifferentCCT.Itis obviousthatthecolortemperaturepreferencesofpeoplearecultureandclimate-related,aswell asdependentoftheprevailinglightingpracticesi ndifferentregions(Miller1998,Ayama etal. 2002).Recently,ithasbeensuggestedthathighc olor

3 LIGHTINGQUALITY

47

temperature light could be used in increasing human alertness (see Ch. 3.5). More research isneededtoconfirmthisandtoapplythesepostulate sinlightingdesign.

UniformityoflightingUniformityof lightinginspacecanbedesirableor lessdesirabledependingonthefunctionof thespace and typeof activities.A completelyuniform space is usuallyundesirablewhereas toonon-uniform lighting may cause distraction and discomfo rt. Lighting standards and codes usuallyprovide recommended illuminance ratios between the task area and its surroundings (EN12464-12002, CIBSE 1997, IESNA 2000). Most indoor lighting design is based on providing levels ofilluminanceswhile the visual systemdealswith lig ht reflected from surfaces i.e. luminances. Foroffice lighting there are recommended luminance rat ios between the task and its immediatesurroundings (EN12464-1 2002, CIBSE 1997, IESNA 200 0). Room surface reflectances are animportant part of a lighting system and affect both the uniformity and energy usage of lighting.Compared to a conventional uniform office lighting installation with fluorescent lamps, LEDsprovideopportunitiestoconcentratelightmoreon actualworkingareasandtohavelightwhereitisactually needed. This provides opportunities to inc rease the energy efficiency of lighting in thefuture.

GlareGlareiscausedbyhighluminancesorexcessivelum inancedifferencesinthevisualfield.Disabilityglareanddiscomfortglarearetwotypesofglare, but in indoorlightingthemainconcernisaboutdiscomfort glare. This is visual discomfort in the presence of bright light sources, luminaries,windows or other bright surfaces (CIE 1987,Boyce 2 003). There are established systems for theevaluation of the magnitude of discomfort glare, e. g. Unified Glare Rating (UGR) (EN12464-12002), Visual Comfort Probability (VCP) (IESNA 2000 ), British Glare Rating system (CIBSE1997), yet thephysiologicalor perceptualmechanis m fordiscomfortglare is not established.Thepresentglare indicesarebestsuitable forassessi ngdiscomfortglare inducedbya regulararrayoffluorescent lamp luminaries fora rangeof standard interiors,and thereareanumberofquestionsrelated to their application in practice. The possi ble problems are related to the definition of theglaresourcesizeandluminanceanditsimmediateb ackgroundluminance(Boyce2003).

Figure3-4. Luminairesandwindowscaninducedirectglare,whi lelightreflectionsfromglossysurfacesandcompu terscreenscaninduceindirectglare.

LEDsaresmallpointsourceswithhighintensities andarraysoftheseindividualsourcescanformluminaireswithverydifferent shapes and sizes. In illuminating the spacewithLEDs special carehastobetakentoavoidglare.

3 LIGHTINGQUALITY

48

VeilingreflectionsVeiling reflectionsarespecular reflections thata ppearon theobjectviewedandwhich reduce thevisual taskcontrast (CIE1987).Thedeterminingfa ctorsare thespecularityof thesurfaceand thegeometrybetween thesurface,observerandsources ofhigh luminance(e.g. luminaires,windows,bright walls). Glossy papers, glass surfaces and co mputer screens are subject to cause veilingreflections.Inroomswithseveralcomputerscreens insidethetaskareaspecialcarehastobetakeninthepositioningoftheluminariestoavoidlumin ousreflectionsfromthescreens.Inusingportablecomputers the viewing directions may change in rela tion to the fixed luminaires and this posesfurtherrequirementsfor lightingdesign.Also,whe nrearrangingtheworkingplacesandgeometryoftheworkingconditions,thepossiblecausesofv eilingreflectionsshouldbeavoidedinthetypicalviewing directions.With proper lighting design, i. e. positioning of luminaires related toworkingareas, it is possible to achieve the samevisibilit y conditionswith less energy thanwith incorrectpositioningofluminairescausingveilingreflectio nstotheworkingarea.

ShadowsShadowsinthespacemaybenegativeinobstructing thevisibilityofcertainelements,buttheycanalsobepositive increatinganattractiveand inte restingvisualenvironment.Whethershadowsareconsideredasvisuallycomfortableordiscomfortabl edependsmuchontheapplication.

Agoodbalancebetweendirectlightanddiffuselig htisimportantinordertoseethewaylightfallson objects. In the quest for more parameters of lig hting quality, it is worthwhile to study theshadowsofobjects ina deeperway: the light side ofanobject, the shadowside, thecast shadowand thepresenceof reflected light.Thiscangive moreconnectionsbetweenscientificandartisticknowledge of lighting qualities.Moreover, for the visual comfort in spaces it is necessary to paymoreattentiontotheshadowing,especiallyforthe comfortofelderlypeopleandvisuallyimpaired.

FlickerFlicker is produced by the fluctuation of light emi tted by a light source. Light sources that areoperated with ac supply, produce regular fluctuatio ns in light output. The visibility of thesefluctuationsdependsonthefrequencyandmodulatio nofthefluctuation.Flickeringlightismostlyasasourceofdiscomfort,exceptinsomeentertain mentpurposes.Forsomepeopleflickercanevenbeahazard tohealth.Flicker fromlightsourcesc anbeminimizedbystablesupplyvoltageorbyusing high frequency electronic ballasts with fluor escent and high intensity discharge lamps(EN12464-12002,CIBSE1997,IESNA2000).

3.4 PsychologicalaspectsoflightPeople perceive their luminous environment through their eyes, but they process this informationwiththeirbrain.Lightscenesarethereforejudged inconnectionwithreferencesandexpectations.Theluminousenvironmentcanbeappreciatedinmany wayse.g.,moreor lessagreeable,moreorlessattractive,moreor lessappropriate to the fu nctionof the space,moreor lesshighlighting thecompany image. Variations of luminances and colors can strengthen attractiveness, triggeremotions,andaffectourmood,theimpactoflighti ngdependingmuchontheindividualsandtheirstateofmind.A lighting installation thatdoesno tmeet theusersexpectationscanbeconsideredunacceptable even if it provides the conditions for adequate visual performance. Unacceptablelighting conditions may impact on task performance and thus productivity through motivation(Boyce2003,Gligor2004).

3 LIGHTINGQUALITY

49

3.5 NonvisualaspectsoflightLighthasalsoeffectsthatarefullyorpartlysep aratedfromthevisualsystem.Thesearecalledthenon-visual, non-image forming (NIF) or biological e ffects of light and are related to the humancircadianphotoreception(Brainard etal. 2001,Cajochen etal. 2005).

The discovery of the novel third photoreceptor, int rinsically photoreceptive retinal ganglion cell(ipRGC), in 2002 has raised huge interest both in t he circadian biology and lighting researchcommunities (Berson et al. 2002). The ipRGC has been found to be the main pho toreceptorresponsibleforentraininghumanstotheenvironmen tallight/dark-cyclealongwithotherbiologicaleffects.Itrepresentsamissinglinkindescribing themechanismofbiologicaleffectsascontrolledby light and darkness. Thus, light can be thought o f as an external cue that entrains the internalclock toworkproperly.Thehumanbiologicalclock drivesmostdaily rhythms inphysiologyandbehavior. These include sleep/wake rhythm, core bod y temperature, and hormone secretion. Itpasses on information regulating the secretion of a lmost all hormones, including nocturnal pinealhormonemelatoninandserotonin,andcortisol.Besi destheshiftingofthephaseoftheendogenousclock by light, there is evidence of the involvemen t of the ipRGCs in pupillary reflex, alertness,mood, and in human performance (Dacey et al. 2005, Duffy and Wright 2005, Whiteley et al.1998).

Thereisevidencethatshort-wavelengthlightisth emosteffectiveinregulatingthebiologicalclock(Brainard and Hanifin 2006, Wright et al. 2001, Thapan et al. 2001). Thus much research iscurrently investigating the possibility to use blue enriched light to affect human responses andbehaviourlikealertnessandmood(Gooley etal. 2003,Lehr etal. 2007,Mills etal. 2007,Rautkylet al. 2009). The effect of light on alertness has been m uch examined, but the mechanismexplainingthedetectedreactionsstillremainsunc lear.

Figure3-5. Lighthasbothvisualandnon-visualresponsesacti ngthroughthedifferentretinalphotoreceptorsandtractsinthenervoussystem.

Thebiologicaleffectsoflightandtheireffectso nhumanperformancearenotyetverywellknown.Aconsiderable amountof researchwork is still req uiredbeforewecanunderstand thenon-visualeffects of light and consider them in lighting prac tice. Research work is needed to generate animproved understanding of the interaction of the ef fects of different aspects of lighting onbehavioralvisualtasksandcorticalresponsesand onhowthebiologicaleffectsoflightingcouldberelatedtotheseresponses.

PhysiologyPhysiology

3 LIGHTINGQUALITY

50

3.6 LightingandproductivityLighting should be designed to provide peoplewith the right visual conditions that help them toperformvisual tasksefficiently,safelyandcomfor tably.Theluminousenvironmentacts throughachain ofmechanisms on human physiological and psyc hological factors, which further influencehumanperformanceandproductivity(Gligor2004).

Figure3-5. Luminousenvironmentandhumanperformance.(Gligo r2004)

There have been several field studies on the effect s of lighting conditions on productivity. Theearlieststudiesweremadeinthe1920s(Weston19 22,WestonandTaylor1926)andindicatedthatlighting conditions can improve performance by prov iding adequate illuminance for the visualtasks. Since then a number of studies have been car ried out. Their results are sometimescontradictory.Forexample,astudyinclericaloff iceworkindicatedthatanincreaseinilluminancefrom 500 lx to 1500 lx could increase the performan ce of office workers by 9% (Hughes andMcNelis 1978), while another study showed that lowe r illuminance levels (150 lx) tended toimproveperformanceofacomplexwordcategorisatio ntaskascomparedtoahigherlevel(1500lx)(Baron etal. 1992).Afieldstudyinindustrialenvironmentmea sureddirectproductivityincreasesintherangefrom0to7.7%duetochangesinlight ing(Jusln2007).Theliteratureincludesmore

Illuminance&

IlluminanceUniformity

LUMINOUSENVIRONMENT

Glare

Luminance&

LuminanceDistribution

CorrelatedColour

Temperature

DaylightLightingSystem

Characteristics

HUMANPERFORMANCE&PRODUCTIVITY

SocialInteraction&

Communication

VisibilityVisual&Task

Performance

VisualAcuity

Arousal MoodEffects

VisualComfort

Acceptability&

Satisfaction

AestheticJudgment

Preferences

Eyestrain

CircadianRhythms

SeasonalAffectiveDisorders

Ageing

DisabilityGlare

SpectralPower

Distribution

DiscomfortGlare

VeilingReflections

ColourRenderingIndex

Flicker SpectrumAmount

ofLight

LightingControl

Direct/IndirectLighting

LightSources

ArtificialLightingControl

DaylightingControl

Param

etersofLuminousEnviro

nment

HumanFacto

rs

Illuminance&

IlluminanceUniformity

LUMINOUSENVIRONMENT

Glare

Luminance&

LuminanceDistribution

CorrelatedColour

Temperature

DaylightLightingSystem

Characteristics

HUMANPERFORMANCE&PRODUCTIVITY

SocialInteraction&

Communication

VisibilityVisual&Task

Performance

VisualAcuity

Arousal MoodEffects

VisualComfort

Acceptability&

Satisfaction

AestheticJudgment

Preferences

Eyestrain

CircadianRhythms

SeasonalAffectiveDisorders

Ageing

DisabilityGlare

SpectralPower

Distribution

DiscomfortGlare

VeilingReflections

ColourRenderingIndex

Flicker SpectrumAmount

ofLight

LightingControl

Direct/IndirectLighting

LightSources

ArtificialLightingControl

DaylightingControl

Param

etersofLuminousEnviro

nment

HumanFacto

rs

3 LIGHTINGQUALITY

51

examples of null results than clear-cut effects of illuminance on task performance, over a widerange of illuminance levels and for a variety of co mplex and simple tasks in officework (Gligor2004).

Theeffectoflightingonproductivityisambiguous .Thedifficultyinfindingtherelationsbetweenlighting and productivity is that there are several other factors that simultaneously affect humanperformance.Thesefactorsincludemotivation,rela tionshipsbetweenworkersandthemanagementandthedegreeofhavingpersonalcontroltothewo rkingconditions(Boyce2003).Withappropriatelightingtheabilitytoperformvisual taskscanbe improvedandvisualdiscomfortcanbeavoided.This can provide conditions for better visual and t ask performance and, ultimately, productivity.The difficulty of field studies in working environm ents is the degree of experimental controlrequired. Several studies have investigated the eff ect of increase in illuminance on taskperformance.However, illuminance isonlyoneof th emanyaspects in the lightingconditions. Inmaking changes to lighting, which lighting aspects are changed (e.g. illuminance, spectrum, andluminancedistribution)andwhether thereareother factors thataresimultaneouslychanged in theworkingconditions(e.g.workingarrangements,peop le,supervisionofwork)needtobecontrolledand analyzed. Recently, several studies are investi gating the effects of light spectrum on humanperformanceandthepossibilitiestouseblue-enric hedlighttoimprovehumanperformancethroughthenon-visualeffectsoflight(seeCh.3.5).

3.7 Effectsofelectromagneticfieldsonhealthandopt icalradiationsafetyrequirementsLightingequipmentandsystemsproduceelectricand magneticfields.Thepotentialeffectsofthesefieldsonhumanhealthdependwidelyonthefrequen cyandtheirintensity,buttheeffectsofhumanexposuretoelectromagneticfieldsarestillnotfu llyknown.

Optical radiation may have hazardous effects on hum an health, eyes and skin. To assess theseeffects the spectral distribution, the size (projec ted size) of the source and the distance from thesourceatthepointofnearesthumanaccessneedto bedefined.TheIEC/CIEStandard62471-1/CIES 009Photobiological Safety of Lamps andLampSyst ems assesses the optical radiation hazardsfromlamps,anarrayoflampsandlampsystems(IEC /CIE2006).Alltypesofelectricallypoweredoptical radiation sources including LEDs are covere d in the standard. Reference measurementtechniques and a risk group classification system f or defining optical radiation hazards are alsoincluded.Thestandardprovidesabasis forevaluat ionofpotentialhazards thatmaybeassociatedwith different lamps and lamp systems. The IEC Tech nical Report 62471-2 Guidance onManufacturing Requirements Relating to Non-laser Op tical Radiation Safety provides basis forsafety requirements dependent on risk group classif ication and related examples (IEC/CIE2008).Similarly to the IEC/CIE standard (IEC/CIE2006) th eANSI/IESNARecommendedPracticeRP-27.1-05 Photobiological Safety for Lamp and Lamp Sy stems covers the evaluation of opticalradiationhazardsfromalllampsandlampsystems( ANSI/IESNA2007).

The emerging LED technology brings powerful and hig h brightness lighting products on themarket. Thewider the field of light (i.e. size of the illumination source) and the brighter (higherluminance)of that source, themorepotential risk it carries for the retina.The ICNIRPStatement(ICNIRP2000) reviews thepotential opticalhazards fromLEDsources and the related standardsand regulations. It is recognized that the determin ation of appropriate viewing durations anddistancesunderdifferentconditionsofusageisne ededforanyopticalradiationhazardassessment.TheStatement recommends thatsafetyevaluationsan drelatedmeasurementproceduresforLEDsfollow the guidelines for incoherent sources (other than laser). It concludes that the futuredevelopmentofapplication-specificsafetystandard sapplicabletorealisticviewingconditionswillreducetheunnecessaryconcernsregardingLEDsafet y.

3 LIGHTINGQUALITY

52

Thephotochemical retinal injury is often referred to as theblue lighthazard (BLH).CIETC6-14TheBlue-LightHazardhasstudiedthemeansandmet hodstoevaluatepotentialBLH.TheoutcomeoftheTC6-14workispublishedunderCIE138-2000 (CIE2000).Thereportproposesatechniqueemploying the ACGIH (American Conference of Governm ental Industrial Hygienists) thresholdlimitvalue(TLV)forgeneraluse.Currently,CIET C6-57ispreparingadraftCIEstandardonthedefinitions and action spectra for two retinal haza rd functions used in photobiological safetydocuments.CIETC6-55isstudyingthedifferentmet hodsofassessingthephotobiologicalsafetyofLEDs.Thisworkreviewstheknowneffectsfromaph ysiologicalstandpointandwilldeterminethedoserelationshipsthatposeapotentialriskfore yeinjuryfromexcessiveirradiation.

The European Directive (2006/25/EC) includes minimu m health and safety requirements foroccupationalexposuretoartificialopticalradiati on.Itintroducesmeasurestoprotectworkersfromrisksrelatedtoopticalradiationanditseffects onhealthandsafety,particularlytotheeyesand theskin.TheDirectiveprovidesmethod todeterminebi ophysicallyrelevantexposure levels forUV-,visibleandIR-radiationtobecomparedwithgiven exposurelimitvalues.

3.8 Conclusions:opportunitiesandbarriersLightaffectshumanbehaviourthroughvariousproce ssesandnewroutescanbefoundinthefuturethroughthenon-visualeffectsoflight.Lightcan actasastimulator(perception,alertness,etc.)o rasan inhibitor (glare,heart ratevariability,etc.). Anychoice in lightingdesignwill thereforehave aconsequence,whichmay sometimes be neglegible, som etimes essential. Increasing the quality oflighting does not mean to use more energy. On the c ontrary, with careful consideration of thedifferent lighting factors andwith proper lighting equipment, the energy consumption of lightingcanstillbedecreasedwhileimprovingthequality oflighting.

In investigating lighting schemes for energy conser vation, it is clear that at the existing level ofknowledge,bothopportunitiesandbarriersinenerg yefficientlightingstrategiescanbeidentified.

3.8.1 OpportunitiesIndoorlightingdesignisbasedlargelyonprovidin gmoreorlessuniformlevelsofilluminancesintheroom,whiletheperceptionoftheluminousenvi ronmentisrelatedmainlytolightreflectedfromsurfacesi.e.luminances. Thusinnovativelightingdesignmethodscouldbein troducedwhichgiveahigh priority to the quality of the luminous enviro nment as our eyes perceive it. The possibleobstaclesandconstraintssetbythecurrentregula tionsforhorizontalilluminationlevelsshouldbeidentified,andwaysfordesigningand implementing more innovative lightingsolutionsshouldbesought.Comparedtoconventionaluniformofficelig htinginstallationwithfluorescentlamps,withLEDsitispossibletoconcentratelightmoreonac tualworkingareasandtohavelightwhereitisactually needed. This will help to increase the lig hting energy efficiency in the future.Simultaneously, LEDs can be used to create interest ing visual environments with varyingluminancedistributionsandshadowswhendesired.

It is clear that the traditional assessment of ligh t on the basis of visibility is not adequate fordescribing the complex, but undeniable, effects lig hting can have on humans. This opens upwindows for designing healthier living and working conditions for people in the future. Thefindings on the interactions of light and the human circadian system indicate that light can havenon-visualeffectsonseveralhumansystemsincludi ngsleep/wakerhythm,corebodytemperature,hormone secretion, alertness and mood. This provide s opportunities to design better lightingconditionsoptimisedforhumanperformanceandwell being,withemphasis,forexample,onlightdistribution and patterns in space and possibly dyn amic light intensity and color. However,

3 LIGHTINGQUALITY

53

considerableresearchworkisstillrequiredbefore wecanunderstandthenon-visualeffectsoflightand consider them in the lighting practice. The und erlying mechanisms of action and thequantificationoflightcharacteristics,including exactspectralcomposition,lightintensity,exposu redurationandpriorlighthistoryremaintobeinves tigated.

Better lighting quality does not necessarily mean h igher consumption of energy. While it isimportant to provide adequate light levels for ensu ring optimized visual performance, there arealwayslevelsabovewhichfurtherincreasesinillu minancedonotimproveperformance.Morelightdoes not necessarilymean better quality of lightin g. Through the use of energy efficient lightingproductsandlightroomsurfacesitispossibleto designenergyefficientandgoodqualitylighting.

NewtechnologiessuchasLEDsandOLEDsofferhigh flexibilityinthecontroloflightspectraandintensities, which enhance their attractiveness bey ond their growing luminous efficacy. Theincreasedpossibilitiestocontrolboththelightf luxesandspectraoflightsourcesshouldallowthecreationofmoreappropriateandcomfortablelumino usenvironments.Visualcomfortrequirementsshould benefit from the increase in the supply of l ight sources and components, leading to bettercontrolof the luminancedistribution.Also, thede velopmentof lightingcontrolsystems,basedonpresence detection and the blending of electrical l ight with daylight, can lead to substantialincreasesinenergyefficiency.

Daylight is a powerful light source, requiring no e nergy to produce. Daylight has a continuousspectral composition and provides good color render ing. Daylight is usually preferred by peopleworking indoors and it can enhance motivation and c an be linked to human circadian rhythms(Dehoff 2002). Daylighting techniques should offer new opportunities for lighting systems inbuildings.Carehastobetakeninutilizingdaylig htinindoorlightingtocontrolitproperlyinord ertoavoiditsglareeffectsandanyveilingreflecti onsresultingfromdirectorindirectsunlight.

3.8.2 RisksReduction of the size of light sources (compactHID lamps, LEDs)may lead to increased risk ofglare.Standardsandrecommendationsshouldbeadap tedaccordingly.

Therecent findingson thebiologicaleffectsof li ghtmay induce temptations touseblueenrichedlight in indoor lighting in order to affect human r esponses. However, a considerable number ofresearchworkisstillrequiredbeforewecanunder standthenon-visualeffectsoflightandconsidertheminthelightingpractice.

Thepossibleadverseeffectsof lightonhealthsho uldbeunderstoodbeforeusinglight to increasealertness and productivity in shift-work. For examp le there is hypothesis that regular bright lightexposureatnight-timeisassociatedwithincreased likelihoodofbreastcancer(Stevens etal. 1997).More research is required on the effects of night-t ime light exposure on human health andperformance.

Photons in the blue range of light are more powerfu l than the ones in the red range, leading topossiblehazardsassociatedwithbluelightwhenno tcontrolledproperly.Theintensityoftheshortwavelengthlight,theviewingdistanceandtheview ingdurationarethedeterminingfactorshere.

Energy conservation measures may lead to the risk o f poor lighting environment to the officeemployees.Poorlightingconditionscaneasilyresu ltinlossesinproductivityofemployeesandtheresultingproductioncostsof theemployercanbem uchhigher than the annualownership costoflighting.

3 LIGHTINGQUALITY

54

References

ANSI/IESNA (American National Standard Institute/ I lluminating Engineering Society of North America), 2007.ANSI/IESNARP-27.1-05:RecommendedPractice forPho tobiologicalSafety forLampandLampSystems Gen eralRequirements.IlluminatingEngineeringSocietyofNorthAmerica WebStore10June2007.

AYAMA,M.,ELOHOLMA, M.,HYVRINEN, M.,EDA,T., KON,D.,MUKAI,K.,KANAYA,S.,HALONEN,L.,2002.WhitenessPerception in Japanese andFinnish underCool andWarmFluorescentLamps. In: CHUNG,R.Y.,RODRIGUES,A.B. J. ed. Proceedingsof the9thCongressof the Internationa lColorAssociation,NewYork,24-29June2001. Washington:SPIE(TheInternationalSocietyforO pticalEngineering)4421,279-282.

BARON, R.A., REA, M.S., DANIELS, S.G. 1992. Effects of indoor lighting (Illuminance and spectra l powerdistribution)ontheperformanceofcognitivetasks andinterpersonalbehaviour:thepotentialmediati ngroleofpositiveaffect,MotivationEmotion,16,1-33.

BEAR,A.R.,BELL,R.I.,1992.TheCSP index:aprac ticalmeasureofoffice lightingquality. LightingResearchantTechnology 24(4),215-225.

BERSON, D.M., DUNN, F.A., MOTOHARU, T. 2002. Photot ransduction by retinal ganglion cells that set thecircadianclock. Science, 295(5557),1070-1073.

BOYCE,P.R., 2003.HumanFactorsinLighting .2 nd ed.LondonandNewYork:Taylor&Francis.

BOYCE, P. R., CUTTLE, C., 1990. Effect of correlate d color temperature on the perception of interiors and colordiscriminationperformance, LightingResearchandTechnology ,22(1),16-36.

BOYCE,P.R.,CUTTLE,C., 1998 DiscussionofVeitchJ.A.andNewshamG.R.,Determi nantsof lightingqualityI:StateoftheScience. JournaloftheIlluminatingEngineeringSociety 27(1),92-106.

BRAINARD,G.C.,HANIFIN,J.P.,GREESON,J.M.,BYRN E,B.,GLICKMAN,G.,GERNER,E.,ROLLAG,M.D.,2001.Actionspectrumformelatoninregulationinh umans:Evidenceforanovelcircadianphotoreceptor . TheJournalofNeuroscience ,21(16),6405-6412.

BRAINARD,G.C.,HANIFIN,J.P.,2006. Photons,clocks,andconsciousness. JournalofBiologicalRhythms ,20(4),314-325

CAJOCHEN,C.,MNCH,M.,KOBIALKA,S.,KRUCHI,K., STEINER,R.,OELHAFEN,P.,ORGL,S.,WIRZ-JUSTICE, A., 2005. High Sensitivity of Human M elatonin, Alertness, Thermoregulation, and Heart Ra te toShortWavelengthLight. TheJournalofClinicalEndocrinologyetMetabolism 90(3),13111316.

CIBSE1997. CIBSECodeforinteriorlighting1994 :Additionsandcorrections1997.ISBN090095364 0.

CIE(CommissionInternationaledelclairage),197 8. Aunifiedframeworkofmethodsforevaluatingvisu alperformanceaspectsoflighting .CIE1978;19-2.

CIE(CommissionInternationaledelclairage), 1987.CIE/IEC. InternationalLightingVocabulary .CIE1987;17:4.

CIE(CommissionInternationaledelclairage), 2000. CIECollectioninPhotobiologyandPhotochemistry. CIE2000 ;138.

CIE(CommissionInternationaledelclairage), 2002. Thecorrelationofmodelsforvisionandvisualper formance.CIE2002;145.

DACEY, D.M., LIAO, H.W., PETERSON, B.B., ROBINSON, F.R., SMITH, V.C., POKORNY, J., YAU, K.W.,GAMLIN,P.D.,2005.Melanopsin-expressingganglion cellsinprimateretinasignalcolorandirradiance andprojecttotheLGN. Nature 433,749-754.

DAVIS, R.G., GINTHNER, D.N., 1990. Correlated color temperature, illuminance level and the Kruithof curve.JournaloftheIlluminatingEngineeringSociety 19(1)27-38.DEHOFF.P.,2002.The impactofchanging lighton t hewell-beingofpeopleatwork. ProceedingsofRightLight5 ,

3 LIGHTINGQUALITY

55

347-351.

DUFFY,J.F.,WRIGHT,K.P.,2005.Entrainmentofthe humancircadiansystembylight. JournalofBiologicalRhythms,20(4),326-338.

EN 12464-1, 2002. Light and lighting Lighting atwork places Part I: IndoorWorkPlaces , European Standard.ISBNnumber:0580411281.

EuropeanDirective2006/25/EC,2006.Ontheminimum healthandsafetyrequirementsregardingtheexpos ureofworkerstorisksarisingfromphysicalagents(arti ficialopticalradiation).OfficialJournalofthe EuropeanUnion,L114,38-59.

FONTOYNONT,M.,2008. Long termassessmentofcostsassociatedwith light inganddaylightingtechniques. LightandEngineering ,16(1),19-31.

GOOLEY,J.J.,LU,J.,FISCHER,D.,SAPER,C.B.,200 3.Abroadroleformelanopsininnonvisualphotore ception,TheJournalofNeuroscience, 23,70937106.

GLIGOR,V.,2004. Luminousenvironmentandproductivityatworkplaces . Thesis(Licentiate),HelsinkiUniversityofTechnology,Espoo.

HALONEN,L.,1993.Effectsoflightingandtaskpara metersonvisualacuityandperformance.Thesisfor thedegreeofDoctorofTechnology,HelsinkiUniversityofTechno logy,ISBN951-22-1845-3.

HUGHES, P.C., MCNELIS, J.F., 1978. Lighting, produc tivity, and the work environment. Lighting Design +Application,8(12),32-39.

ICNIRP(InternationalCommissiononNon-IonizingRa diationProtection),2000. StatementonLight-EmittingDiodes(Leds)andLaserDiodes:ImplicationsforHazardAs sessment.HealthPhysics78(6):744-752

IEC(International Electrotechnical Commission), 200 6. Photobiological Safety of Lamps and Lamp Systems . DualIEC/CIEStandardIEC62471-1/CIES009.

IEC(International Electrotechnical Commission), 200 8. Photobiological safety of lamps and lamp systems . Part 2.Guidanceonmanufacturingrequirementsrelatingto non-laseropticalradiationsafety.

IESNA(IlluminatingEngineeringSocietyofNorthAm erica)2000. TheIESNALightingHandbook ,9 th ed.NewYork:IESNA.

JUSLN, H., 2007. Lighting, productivity and preferrd illuminances field studies in the industrial environment.Thesis(PhD).HelsinkiUniversityofTechnology.

KRUITHOF,A.A.,1941.TubularLuminescenceLampsfo rGeneralIllumination. PhilipsTechnicalReview ,6(3),65-96.

LEHR, S., GERSTMEYER, K., JACOB, J.H., FRIELING, H. , HENKEL, A.W., MEYRER, R., WILTFANG, J.,KORNHUBER,J.andBLEICH,S.,2007.Bluelightimpr ovescognitiveperformance. JournalofNeuralTransmission ,114(4),457-460.

LOE,D.L.,ROWLANDS,E.,1996. Theartandscienceof lighting:astrategy for lig htingdesign. LightingResearchandTechnology 28(4),153-164.

MILLER,N.J.,1998. Arecipeforlightingquality,ProceedingsoftheF irstCIESymposiumonLightingQuality .CIEx015,40-47.

MILLS, P.R., TOMKINS, S.C., SCHLANGEN, J.M., 2007. The effect of high correlated color temperature off icelightingonemployeewellbeingandworkperformance . JournalofCircadianRhythms ,5,2.

RAUTKYL,E.,PUOLAKKA,M.,TETRI,E.,HALONEN,L. 2009.Correlatedcolortemperatureandtimingofli ghtexposure; their effects on daytime alertness in lec ture environments, to be published in Journal of Light and Visual

3 LIGHTINGQUALITY

56

Environment.

REA,M.S., OUELLETTE,M.J., 1991. Relative visual p erformance: a basis for application. Lighting Research andTechnology 23(3),135-144.

STEVENS,R.G.,WILSON,B.W.,ANDERSON,L.W.,1997. Themelatoninhypothesis:breastcancerandtheuse ofelectricpower,Columbus,OHBattellePress.

THAPAN,K.,ARENDT,J.SKENE,D.J.,2001.Anaction spectrumformelatoninsuppression:evidence fora novelnon-rod,non-conephotoreceptorsysteminhumans. TheJournalofPhysiology, 535(1),261-267.

VEITCH, J.A., NEWSHAM,G.R., 1998. Determinants of l ighting quality I: State of the Science. Journal of theIlluminatingEngineeringSociety 27(1),92-106.

VEITCH, J.A., 2001. Psychological processes influen cing lighting quality. Journal of the Illuminating EngineeringSociety 30(1),124-140.

WESTON,H.C.,1922.AstudyoftheefficiencyIfin elinen-weaving, IndustrialFatigueResearchBoard ,ReportNo.20,London.

WESTON,H.C.,TAYLOR,S.K.,1926.Therelationbetwe enilluminationandefficiencyinfinework(type-s ettingbyhand),FinalReportofthe IndustrialFatigueResearchBoardandtheIlluminat ionResearchCommittee ,London.

WHITELEY, S.J.O., SAUVE, Y., AVILES-TRIGOEROS, M., VIDAL-SANZ, M., LUND, R.D., 1998. Extent anddurationofrecoveredpupillarylightreflexfollow ingretinalganglioncellaxonregenerationthrough peripheralnervegraftsdirectedtothepretectuminadultrats.Exp .Neurol,154,560-572.

WRIGHT, H.R., LACK, L.C., PARTRIDGE, K.J., 2001. Li ght emitting diodes can be used to phase delay themelatoninrhythm. JournalofPinealResearch ,31,350-355.