sylvania understanding lighting brochure 1988

7/28/2019 Sylvania Understanding Lighting Brochure 1988

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Light ng affects every indiv duan one way or anothel from the home-owner to the commercial offtce bu ldingmanagel from the factory foreman tothe drugstore cashier, from the ightingscientist to the ocal electrical contrac-tor. What makes ghting unique is that,with this widespread impact, it rs anindustry based on science and techno ogy. The deve opment and manu-facturing o{ ight sources rnvolves thesc ences of physrcs and chemistry,the measurement of light and color'equi'es sopl'isticated pholonetrictechniques and devices, and theaccurate caicu aton o{ rghting uti zesdetailed mathematica procedures.

This combinat on of a technologybased industry w th such a broadmpact creates a need for educat on.Since many of the peop e nvo ved inthe ighting ndustry have a limtedtechn ca background, the scienceand technology underlyrng much ofthe f eld of lighting needs to be com-munlcated in such a way as to prornotegreater understand ng and better app ication. This need exists for a wrderange of people, f rom a saLespersonfor an electrical d strlbutor to an interiordesigner: from an owner of a smallretail store to a facilities manager for aarge corporation.

The purpose of this brochure jsto fu f il thls need. lt is ntended for areader who has an interest in ightng,but who has lim ted background knowl-edge. The brochure defines some ofthe basic term nology used n the lighrrgrndust'y. ' arso g ves a1 overvie\\of the physical propert es which char-acterize light and color, and descnbesthe various types of light sources wh chare available today. The informat onpresented here wi I hopefully equip thereader to 'na^e "no'e ilo'ned decis ons regarding ghting, no matterwhat h s or her part cular area ofnterest may be.


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When most peop e want todescribe the amount of ghtthataght bulb or other lght source pro-duces the first quant ty that comes tomind s watts lf a table lamp in theI ving room does not prov de enoughlght, a hgher wattage bu b s pur-chased. Thus many peop e may thinkof \,,/attage as a measure of ight output.However, wattage s actua yameasureof eectr ca po\'ver tdescrbestheamount of power going n nottheight coming out.

The word 'lamp' s used to ind cateincandescent f uorescent or other ightsources To descr be ight output theo- r'ed " lumens. l.le.-mel ameasure of the totai ght produced bya amp t measures the quant ty of ght,but does not indicate the direct on ofight at ai . The lumen rat ng va ue canbest be thought of as the tota surn ofa lthe licrht (in a I directlons) that theamp produces.By estab ishing a rat o between theiight output (lumens) of a amp andthe power input (watts), an effjc ency

1 ea'L d Cd- be d^' r^d. Tl . 'a o >ca led the lumen-per-watt rat o orLPW The LPW value s s milar in someways to a miles-per-gal on rating for acar, s nce t expresses what you canqe ou, of o la.rp ir le r. ol ,r'raL i-put into t. A higher LPW ndicates thata amp LS able to produce more lightfor the same amount of powef andthus is a more eff cient I ght source.LPW is of ten referred to as a measureof 'btf cacyl' since it is a rat o of twodifferent units (umens and watts), andnot a percentage as a true eff ciencymeasure would be.

FOOTCANDTXS VS. CANDTEPOTTTRWatts, umens and LPW al describebasic character st cs of a tght source.But they do not provide any nformatton'ega dr.to r^,. gr lt.tg - a 'oo- -oexamp e, f we want to know how muchoht is fal nct onto a desktop in anoff ce, we need to def ne a new un tthe footcandle.The footcand e is a measure of thequant ty of lqht ( lluminance) wh ch fa isonto a surface. Thus the light ng leven a room rs usual y descr bed as a certa n footcand e evel The I lumrnat ngf -orr-or r o So. ^-, o \o tl l-e..copub rshes tables "vhich prov/de recom

mended footcand e eve s for var oustypes of rooms and tasks Someof the-ro r o'.1 r 6r, ;.od o l-- .e,eto'rr^1d.,-o' d F . Lt ra. zed nTable 1.F=ootcand e is often confusedwith candlepower. Candlepo\ii er or."^deas do. oe 1,. ,gl L tp .. ,oad-p ? a(a d.-c o'. ameasure of the ghtsource tsef.Thefootcande, on the other hand isameasure of the lghtrng n a room. Thereforet is ncorrect to ta k about "cand epower on the desk ' or 'band epo\,,jerat the task," s nce these phrases rea yrefer to footcand es

$BLEIIES IILI]MINANCE VATUES

Ranges olllluminances(Footcandles)Public spaces with dark surroundingsSimple orientation for short temporaryvisitsWorking spaces where vrsual tasks areon y occasional y performedPerformance of visual tasks of:

High contrast or large sizeMedium contrast or small sizeLow contrast or very sma I sizeLow contrast and very sma I sizeover a pro onged period

Performance of very prolonged andexacting visua tasksPerformance of very special v sua tasksof extremely ow contrast and sma size

2-3-5 FC5-75-10 FCt0-15-20 FC

20-30-50 FC50 75-100 FC

100-150-200 Fc200-300-500 FC500-750 1000 FC

1000 r500-2000 FC


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Candlepower differs from lumensin that a cand epower measure a wayshas a certa n direction associatedwith it, whereas the umen rating for aamp is the general tota light output inal directrons. Cand epower va ues forany given amp will change depend ngon the direction. Figure 1 illustrateshow the angles are determ ned whena cand epower rating s g ven. Forexample,'benter-beam candelas"expresses the liqht ntensty in thecenter of the beam of ght producedby a lamp, or the ght intensity at the0" angle.

When dea ing w th reflectorizedlamps, PAF lamps, or MR amps,(see Figure 14), the terms "beamangle" and 'f ield angle" are oftenused. The beam angle is def ined astl'e angle where lhe candlepowerrreasu'e is eqral Lo 500 o ol lhe na,,i-rrun cand epowe' -1-s 1s 6 3ngle is

CenterbeamIllusbation of Candlepouer Rating Angles

rIGUB' 1the ang e where the candlepower isequal to 100/o of the maximum candle-power. These two measures, jl ustratedin Figure 2, are often used to evaluatehow w de or narrow the beam of lightproduced by a certain lamp wil be.For example, the beam angle of a'spot" lamp type will be much smallerthan that of a 'Tlood" amp, ind catinga mrch narrower beam.

WATTSXHOURS=ENERGYA f na concept which must beunderstood rs that of energy. Manypeople think of wattage as a measuof eneroy, but as discussed previouwattage measures power nPUt, noenergy consumption. Energy is mesured by watt-hours, or kiowatt ho(kWH). lr is tlJS a corrb rat or o[ bpower npLr (war-s) and tirre (hou'

This def jnition is significantbecause the lighttng user can saveenergy by controlling both connecload (wattage) and the t me of opertion. ln fact, it is sometimes true thahlgher connected oad may providg'eater Iexb ty 'n lerns of swtchard controls. wh.ch g ves lhe lserqreaLe cortrol ove lhe tine aspPc6rerqy corsutrptior. I hrs. arrloLgreducing the wattage of a ightingsystem will indeed help to conservenergy, it is the management of tenergy be ng used which ts criticaFrom this perspective, bothwattage and time of use must becarefulLy evaluated ln any applicato


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mm u'dtt n mRadiant Energ/ Spectrun

350 400 450 500 550 600 650 m0 7s0 800

(xlfix'4 Visible Light Spectrum

flcry WHAI IS UGHT?To rea ly understand lghting, the

'i'st qrestio'r wh cl' needs answeringis, 'What is igh?"Probab y the sirnp esr desc'ipt orof light is the phrase 'Visua ly evaiuatedradiant energy." In other words, ght sa form of radiant enerqy, lust as radiowaves and X-rays are forms of radiantenergy. But what makes rght uniquefrorr othe. 'o'ns of 'ad arr e'rerqy isthat the human eye rs sensitive to thisform or ere'gy and responds lo I.Figure 3 shows the spectrum ofthe various types ol radiant energy.As this frgure il ustrates, the types of

energy are described by the r waveengths, and the human eye respondsto a limited band ol wavelengths alongthis spectrum. lt is this band of wave-engths which is ca led visible lght.

Breahdoun of lYhite Lighl


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\,iavelengihs (Nanometers)Cool White SPD Curft

WHITT I,IOHTAn expanded vjew of th s bandof v sible light energy is shown inFigure 4. Each wave ength of energyis associated w th a certain co or sen-sat on, and "wh te ight ' s s mp y thesummation of var ous colors or wavelengths of light. The simple pr smexper ment performed in most highschoo science classes (Figure 5)demonstrates this pr ncip e, by div dingwh te ight into its various wave engthcomponents.

Understanding that light s madeup of certa n wave ength compofentsis important in understand nq the natureof the light produced by amps. The

ight output from a lamp can, ke sunight, be broken down into its ndrv duawave ength components. For exampleFigure 6 shows the wave ength composition of the ight produced by a CooWhite fluorescent amp.SPD

A graph of this type s caled a"spectral power distributioncurve," oT an SPD. This name isder ved from the fact that the graphil ustrates the distribut on of powerproduced by the amp, at each wave-length (or coior) across the spectrunrFigure 7 shows the SPD s for someother common amp types, al of wh care cons dered Wh te' light sources.

Eramples ol Othet SPD Cu res f$sBI'7INCANDESCENT ANDTUNGSTEN HALOGEN ocTRoN"4100

METALARC' COATED

DESIGNER "830"

Uihvelenglhs (Nanometers) l bvelenqths (Nanometers)

LUMALUX"

$bvelengths (Nanometers) l/llavelenEths (Nanometers)


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COLOR IS HOIY YOU LIGHT IIAlthough an SPD curve f ul ydescribes the co or characteristics ofthe lqht produced by a lamp, it s diffcult for the normal ighting user to derivemuch mean ng from such a curve.nstead, bryo measures of ctht sourcecolor have been established, and arecommon y used to describe the colorcharacter stics of lamps. These measures are color temperature and thecolor rendering index or CRl.

Co or temperature describes theactual color appearance of the lightproduced, in terms of its apparentwarmth or coolness.CRI is a measure of how the lampinfluences the color appearance ofthe objects which are being il uminated.The relationship between these two'neasJres is sl'owr schematical y inFigure 8.

THX IIDIVIN SCAI.En def ining color temperature, aefe'erce solce s used which sknown as the blackbody radiator.

This source can be thought of assimply a p ece of meta wh ch isconplelPl) b acl. u her co d. Dassiagelectricity through this piece of metacauses it to heat up. unt eventual y itbeg ns to glow When t f irst begins toglow, the light be ng emitted is redorange n appearance. As the meta isheated to progressively hrgher tem'peratures, the co or appearance w Ish ft to orange, then yel ow, and even-Lua ly wrI oe olJe o' b Le \ hite atextreme y h gh temperatures.

At any po nt dur nq th s process,the actual temperature of the b ack-body could be measured. For co ortemperature measurements, the Kelvinscale is used, which s def ned asdegrees Celsius plus 273. Thus, acertain Kelvin measurement can beassociated with the various co orappearances of the blackbody ast is heated

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CORREI,JIITD COI,ORTEMPERAIURECo or temperature is a measure-ment of temperature on y when thesource berng considered s the black-body rad ator. For other light sources,the term "correlated color temper-ature" s used. Thus, a ight sourcewh ch has a corre ated co or tempera-ture (CCT) of 4100 Ke vin, such as thecool white flourescent lamp, is simiarn color appearance to the blackbodyradiator when t is heated to 4100K. Astandard ncandescent amp, with aCCT of 2700K, ls sim ar n co orappearance to the b ackbody whenheated to a temperature of 2/00K.A photograph of the appearanceof the ght produced by these twoght sources is shown rn Figure g.Figure 10 shows the range of corre-ated co or temperatures for typicacommercia lamps.

\

F$a*J'solor appearance co nparison betoeenan incandescent lanp (2700K. uarn) andacool bhite lluorescent lanp (1200K cool),

Relationship Behoeen CRI and Color Temperalure

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WARM UGHI VS. COOI, UGHTAs described above, at low colortemperatures the blackbody sourceemits a red or red-orange light. Psy-cholog ca ly, these co ors are usua lyconsidered to be 'Warm" in appearance; thus, lamps with low correlatedcolor temperature (be ow 3200K) arethought of as 'Warm" ghtsources.Conversely, at high color tempera-tures the b ackbody gives off a b ueor b ue-white light, which is psycho-

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ogrca ly considered 'boo 'l Lampswith correlated color temperaturesabove 3900K are thus 'bool" lightsources.Lamps with CCT ratings betweenthese values (3200-3900K) are con-

s dered intermediate sources. Thesed vis ons are sometimes confusing,since h gh temperatures are norma lyassociated with 'Warm," and low tem-peratures with 'bool." ln the case ofthe color temperature scale, theseassociations are the exact oppositeof what might be expected.

fiE COTOR RXNDtrRING INDEXAlthough correlated color temperature describes the actual appearanceof the light being produced by a lampit gives no indicat on of how the lampwi I affect the color appearance ofobjects being lghted by the lamp.This second considerat on is usual yat least as important as the colorappearance of the amp itse f .

For example, Figure 11A showstwo ditferent light sources which haves milar CCT values, and so are simiarin terms of their co or appearance.9000

-85oo

-

NoFrFiLcFrriBLUE SKY8000

-7500

-7000

-

rl j1r F.' :''

CAPSYL TE'TUNGSTENHALOGEN LAIi/P

DAYLIGHT

WABi,4 WH TEFLI]OFESCENT LAMP

H GH PBESSURESOD IJM LAMP

6000

--..^'rMEBCURY

LAN4P5500

-5000- CLLAB [,IfTAiHALIDF AMP

4000

-cooLWP -FFLUOFESCENI LAMP

3500

-

The color appearance ol tuo lightsowces ofthe sdme conelaied colortenDeraturc Ls sinilar. as shoun ,'nofil)"),y:x,::';i!!rrri!,i{i,r.ti"!!ir:,iiicaltf, as shoun belob. This denonstratesthe need lor a neasure oflhe colot rcnde ngproperties ofa [amp.

40 WATTNCANOESCENT2500 _2000

-CANDLE

1500

-The Correlated Color Tenperature Scale

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The eighl standafucolors used to detetnine CRI aalues.

Howeve4 simply knowing that theselamps are s mi ar in co or appearancegives no indication of how they w Laffect co ored objects.As il ustrated jn Figure 118, theeffect of these two light sources onthe appearance of the same redobject is surpris ngly different. Thus.the CCT color measure does notprovrde enough nformation by itself ,and we need a second measure todescribe how a amp wil affect theco or appearance of objects. Thecolor rendering index, CR ,performs this f unction.

f$tJBJ't2,EIGHT SIANDARD COLORS

S nce the CRI measures the effectof a light source on the co or appearalce ofobjects. -he firs- s-ep 1 de.i\ ^gthis measure is to def ne some standard colors. The internationa ght ngcommunity has sett ed on eight standard colors for use n determ ning theCRI rat ng for amps. These eightcolors are depicted n Figure 12.

To detern r ne the CR of a particu ararP. the co 61 3PPoa ance o[ ll-esaeight standard colors is f rst eva uatedunder the blackbody reference sourceat the same co or temperature as thelamp being invest gated and a CRIvalue of 100 is assigned to the apoear-ance of each of the eight co ors.

The eight co ors are then eva uatedunder the lamp in quest on, and theirco or shrft from the appearance underthe blackbody s measured a ong ascale from 0 to 100. The pub shedCRI va ue represents the average ofthese eight nd vidua CR values.A few mportant observations canbe made from this discussion. A CRvalue of 100 does not mp y "ideal"color render ng ab ity, t s simply thereference measure used. Fortunate ythe blackbody reference source doestend to render co ors as people expectthem to appear, so that in genera a100 CR is interpreted as exce lentcolor render ng


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TUilGSTEIU HAI.OGDN I,A.IUPSA special family of lamps wasdeveloped to alleviate the problemof tungsten evaporation. These lightsources, known as "tungsten halogen"lamps, utilize halogen elements suchas bromine and iodine to minimizebJlb blackening by creatirg a cleanirgcycle within the lamp. Basically, thehalogen prevents the tungsten fromdepositing on the bulb wall, andrnstead, redeposits i1 onto thefilament.The main advantages aremaintaining most of a lampsinitial brightness over the li{e ofthe lamp and longer lamp life.

Because quarlz glass is sometimesused for these lamps, many peopiere'er Io I rngsten halogea sourcessimply as quar2 lamps.

..A IJLIUP-Mtf, IN-A-LA.lltP'Traditionally, tungsten halogenlight sources were mostly available ina tubular shape. But today, tungstenhalogen lamps are avaihbb in manyof the standard incandescent shapesby using a small capsule within thebulb itseli. Lamp types such as theSylvania Capsylite@ family use this tech-nolooy to achreve the advantagesof better lumen maintenance andlonger life.

LOWVOIIAGE IA"ITPSAnother variation in the traditionaoperating parameters o{ incandescentlamps is the increased popu arily oflow voltage sources. A lamp which isdesrgned for low voltage operationhas a shorter thicker {ilament. Thistranslates nto better optical contro

when the lamp contains an integralreflector (such as a PAR or MR lamp,see Figure 14).Low voltage operation may beachieved via two main methods: eithea transformer is used external to thelamp, or a diode is placed within thelamp to reduce the voltage to'lhe frla-ment. In either case, the advantagesof low-voltage operation are realized.

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Fluorescent lamps operate on theprinciple of energizing a gas. A fluores-cent lamp contains a small amount oflow-pressure mercury vapol whichproduces ultraviolet radiation when anelectrical arc is passed through thelamp. This ultraviolet radiation is in turnabsorbed by a phosphor coating onthe lamp, which then produces visiblelight (see Figure 15).The wavelength composition of thelight from the lamp, and thus its colorproperties, are determined by thechemical elements used in the phos-phor. ln addition to the mercury vapola fJuorescent amp also contains aninert gas fill, usually erther argon.krypton, or neon.TWO NDQINREMDI{TS

With any type of gaseous dischargelight source such as a {luorescentlamp, two electrical needs exrst.First of ali, n order to establish an

electr cal arc through a gas atmosphere, an initial voltage surge rsrequired. This suroe is only neededto start the amp.Secondly, once the lamp is started,the gas atmosphere offers a decreas-ing amount of electrical resistance.This means that, if the current avail-able lo the lamp is not contro led, the

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lamp will continue to draw more andmore current, until it burns itsel{ out ina short period of time.THE BAIIJISTBecause of these two concerns,an auxilrary prece of equipment knownas the ballast is required for gas d s-charge light sources. The ba last servestwo main purposes: lt provides thenitial voltage surge needed to startthe lamp, and it limits the amount ofcurrent available to operate the amp.

Bal asts wh ch have been approvedby the Cert f ied Ba last l\lanufacturers(CBM) assure the user of certain per-formance character strcs. Since thebal ast helps to determine the f nalght output of the ohtino system, anon-CBM ba last may provide manyess umens than the user wou d expect.

PHOSPHOR TT,CHNOLOGYThe aspect of f uorescent lampdevelopment which has changedmost raprdly ls phosphor technology.Tradit onal f uorescent lamps suchas the Cool White lamp use a singlecoating of halophosphor materra . Wrththis type of technology, a trade offmust be made between energy eff,

:.";,:15;::?::f :q::,$ J: ",""#"as n he Cool Whrle Deru;e lanp. tl-e.f Iciercy o' rhe grtsolrcerusr becompromised, result ng in lower output.A newer technology whichaddresses this concern is the useof rare earth phosphors. These phos-phor types give the new f uorescentlamp types both high eff iciencies andgood color properties. To ut ze thesenew phosphors economically, a doub e-

it *q SrWntu.ill.H. .'

".1rr u\",t,1 ,-in h /,/.,,isible Light' /' // Ullr.aviolel\,\\i I /,'/7 Radiation

Mercury Atom - aeFrcUBD r"Pr nc ip lei of F uoresce n t Opera I o n

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coat phosphor process was devel-oped by GTE Sylvania. This processcombines a base coat of the standardhalophosphor with a second coat ofthe rare earth phosphor. This combi-nation is used in manufacturing moreadvanced Sylvania lamp types.

This technology is illustratedin Figure 16. Lamps such as theSylvania Octron@ family and theSylvania Desigre.o Series rrse trisnew technology to make possiblefluorescent lamps which exhibit bothhigh eff iciencies and good colorcharacteristics.TS AJIll TT2 IIIJUPS

Another area of new developmentin fluorescent lampsis in the size of thelamp itself. For generallighting applications,reduced diameter f lLro-

rescent lamps have become quitepopular. These lamp types, having adiameter of one inch (T8) as opposedto the traditional one and one-half inch(T12) diameter lamps, offer improvedeff iciency and better optics within afixture.

Furthermore, because the totalarea of the bulb is less. the rare earthphosphors can be used more eco-nomrcally. Sylvanra Octron and OctronCurvalume@ lamps are examples ofsmaller diameter fluorescent sourceswhich may be used in traditional gen-eral lighting applications.For other types ol applications, com-pact fluorescent lamps are now widelyused. Lamps such as the Sylvania TwinTube and Double Tivin Tube, originallythought of as options for replacingincandescents, are now also usedfor many task lighting, downlighting,and decorative purposes. These ampsexhibit much higher eff iciencies thanincandescent lamps.

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Sp silw4!lAS\]PER\A'!L'O @SraI:3"1\'t"; ,,$,rt ifl,fti#*ut "b

Single Coat

rtcuBE 1:Phosphor Technologl/

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Further ref inements of the lightproduced may be made through theuse of phosphor coatings. For e>ample,Sylvania Metalarc@ metal halide lampsare available in cleal coated, and 3Kcoated versions. wilh each type havingdif{erent color properties. This varietyallows Metalarc lamps to be well-suitedto many difierent commercial andindustrial app cations.Because of their high eificiencyand the intensity or brightness of tra-ditional metal halide lamps, they havebeen widely used in commercial

interiors where high cetlings call forlamps with high light output, longlamp life, and economical lamp oper-ation. A major trend in the develop-ment of these light sources has beento produce low-wattage metal halidelamps for such applications as retaillighting, where the features of highe{ficrency, good colol and compact-ness are important. The Sylvaniafamily of low-wattage medium baseand tubular Metalarc lamps is anexample of this trend.

The family of light sources knownas high intensity discharge (HlD) lampsincludes mercury vapor lamps, metalhalide lamps, and high pressuresodrum lamps.These light sources all produce lighti.r the same basic rnanne., by ere'g'z-ing a gaseous arc stream which oper-ates under increased pressures. Theaddition of various elements to the arcstream affects the efficiency and colorproperties of the light. These threemain types are thus differentiated bythe makeup of the arc stream, asdescribed belowMERCURY VAPOR IIIJTIPS

As the name implies, mercuryvapor lamps produce lighl by ene,2-rng mercury gas. At low pressures,mercury vapor produces mostly ultra-violet energy, as described {or fluores-cent lamps. Howevel the increasedpressure used in mercury vaporlamps shifts the energy produced intothe range oJ visible light. Althoughsome ultraviolet light is still produced,the glass outer jacket on a mercuryvapor lamp effectively f ilters thisUV energy.Mercury amps were the first HIDtype manufactured, but the usefu -less o[ lhese lorg 'fe lamps -oday islmited by their ower eff iciency andpoor color properties.IIIDTAI HAIJDE III"MPS

An improvement in H lD technologycame about through the deve opmentof metal halide lamps. Although mercL'y vapo'is srll used as lhe naillight produc ng element, certain chem-ica add tlves (halides) are used inthe arc stream to provide excelentcolor quality for many commerc al,industrial and outdoor applicationsplus outstanding lamp eff iciency.

ligLfitlAIIVAJIIAGES & IDRAWBAGKSOF MAJOR LAMP IYPES

Lamp Type Advantages Drawbackslncandescent

Fluorescent

Metal Halide

H gh PressureSodium

. low initial costo small size. excellent color. variety of shapes. simple circuitry. ease o{ dimming. higher efiiciencies. long life. variety ot colorso low brightness. low operating temperature. diffuse rght source. high eff icrencies. long life. reasonable optical contro. ow operat ng cost. good co or properties. ong life. very h gh ef{ ciencies. reasonable optical contro

. very low operat nct costs. hgh umef mantenance

. low efiiciencies. high heat output. high operating costs. short life. glare potentlal

. higher initial cost. temperature sensitivity. limited optical control. auxiliaries needed

. high initial costo auxiliaries needed. start-up & re-str kerequirements. co or cons stency. giare potential

. high initia cost. auxiliaries needed. start up & re-str kerequirements. poor co or propert es. glare potential

14


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IIIGH PRXSSTJRE SIilIIUM I.II"IUPSThe third type of HID source, highpressure sodium lamps, were devel-oped primarily to improve upon theefficiency available in other lightsources. Aga,n. rrercu.y is used inthe arc stream but in this case sodium

ls also added. This mixture pro-vides the highest eff icaciesavailable in HID lamps.A ceramic arc tube isneeded instead of standardglass due to the use of so- n.-drum. The presence of & -r -sod un in lhe arc streamresults in the energy pro-duced being mostly inthe yellow portions ofthe spectrum.

The excellent eff iciency and long,24,000 hour life of high pressuresodium lamps like the SylvaniaLumalux@ family make them suitablefor outdoor and industrial uses, buttheir relatively poor color propertieslimit their usefulness in commercialinteriors.

A special type of hrgh pressuresodium lamp is also avaiable toreplace existing mercury vaporlamps. Lamp types such as theSylvanra Una ux@ family are1 designed to operate on reactormercury ballasts, and allowthe user [o ircrease lhe efli-ciency of his lighting system bysimply replaclng the mercurylamps with this special type ofhigh pressure sodium lamp.

Since all HID lamp iypes are gas-eous discharge light sources, theyrequire ballasts {or operation. The balast must be designed specilically fothe lamp type and wattage being usedWARIII.UPTIME

Another unique characteristic ofHID lamps is that they require a certaiperiod of time to warm up to f ull lightoutput.This is especially important in are-strike situation, where the power 10the lamp has been momentarily interrupted. ln this case, a jew minutesmay be required before the lamp willcome back on, and then it will take afew nore m;nJtes bdo.e the systemat full brightness. Thus, provisrons {oremergency lighting must be made byusing a back-up tungsten halogensystem or a specia liqht sourcesuch as the Sylvania LumaluxStandby lamp.Low pressure sodium lightsources are a special type, in whichsodium is used as the only element inthe arc stream. Although this providevery high efiicacres, it also producesa monochromatic yellow light. Withthis type o{ light, few colors can bereadily distinguished. Because ofthese qenerally unacceptabie colorproperties, low pressure sodiumlamps have very limited application.Table 2 provrdes an overv ew ofthe features and drawbacks for eachof the lamp families described aboveTl'is tab e can be helplul n co'npa'rnqthe var ous types and consider ngwhich might be best surted for anyspecrfic app rcation.

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Although much o{ the lightingindustry is technology based, the{.Lrdamenta s o' lightirg are farrlystraightforward and easily understood.Knowledge o{ the types o{ light sourcesavailable, the rnethods used to describethe color properties of those sources,and the basic terms used to describethe application of light should helpthose jnterested in lighting to makebetter decisions regarding their ownspecific needs. Hopefully, this bro-chure is a step toward that end.

IJSI OF FIGURDS1. lllustration oi Candlepower Rating Angles2. lllustration of Beam Angle and Field Angle3. Radiant Energy Spectrum4. Visible Light Spectrum5. Example o1 Prism Breakdown of White Light6. Cool White SPD Curve7 Examples of other SPD Curves8. Relationship between CRI and Color Temperature9. Comparison of Cool White and Incandescent Color Appearance

10. The Correlated Color Temperature Scale11A, 11B. lllustration: Same CCI Different CFI12. Eight Colors Used in CRI Measurement134, 138. lllustration: Same CRl, Dilferent CCT14. Incandescent Lamp Shapes15. Principles of Fluorescent Operation16. Phosphor Technology

IJST OT TABI,N.S1. IES llluminance Values2. Advantages and Drawbacks of Major Lamp Types

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sylvania understanding lighting brochure 1988

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