1、IES TM-1-12The Five Lightinullg MetrinullnullIES TM-1-12The Five Lighting MetricsUpdate authored by:Daniel nullogersInullF InternationalOriginal Author:Joseph B. MurdochPublication of this Technical Memorandum has been approved by the IEnull.nulluggestions for revision should be directed to the IEnu
2、ll.IEnull TMnullnullnullnullnullCopyright 2012 by the Illuminating Engineering Society of North America.Approved by the IES Board of Directornullnull nullune 1null 2012null anull a nullrannullaction of the Illuminating Engineering Society of North America.All rightnull renullerved. nullo part of thi
3、s publication may be reproduced in any formnull in any electronic retrieval system or othernullisenull nullithout prior nullritten permission of the IEnull.Published by the Illuminating Engineering nullociety of nullorth Americanull nullnullnull nullall nulltreetnull nullenull nullornullnull nullenu
4、ll nullornullnullnullnullnullnull.IEnull nulltandards and nulluides are developed through committee consensus and produced by the IEnull Office in nullenull nullornull. nullareful attention is given to style and accuracy. If any errors are noted in this documentnull please fornullard them to nullita
5、 nullarroldnull nullirector of Technologynull at the above address for verification and correction. The IEnull nullelcomes and urges feedbacnull and comments. InullBnull null nullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnull.nullrinted in the nullnited Statenull of America.DISnull
6、LnullIMEnullIEnull publications are developed through the consensus standards development process approved by the American nullational nulltandards Institute. This process brings together volunteers representnulling varied vienullpoints and interests to achieve consensus on lighting recommendations.
7、 nullhile the IEnull administers the process and establishes policies and procedures to promote fairness in the development of consensusnull it manulles no guaranty or nullarranty as to the accuracy or completeness of any information published herein. The IEnull disclaims liability for any innullury
8、 to persons or property or other damages of any nature nullhatsoevernull nullhether specialnull indirectnull consenulluential or compensatorynull directly or indirectly resultnulling from the publicationnull use ofnull or reliance on this documentIn issuing and manulling this document availablenull
9、the IEnull is not undertanulling to render professional or other services for or on behalf of any person or entity. nullor is the IEnull undertanulling to perform any duty onulled by any person or entity to someone else. Anyone using this document should rely on his or her onulln independent nulludg
10、ment ornull as appropriatenull seenull the advice of a competent professional in determining the enullercise of reasonable care in any given circumstances.The IEnull has no ponullernull nor does it undertanullenull to police or enforce compliance nullith the contents of this document. nullor does th
11、e IEnull listnull certifynull test or inspect productsnull designsnull or installations for compliance nullith this document. Any certification or statement of compliance nullith the renulluirements of this document shall not be attributable to the IEnull and is solely the responsibility of the cert
12、ifier or manuller of the statement.IEnull TMnullnullnullnullnullnullontents1null LUMInullUS FLUnullnull null. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12null LUMInullUS InullEnullITnullnull Inull. . . . . . . . . . .
13、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1nullnull ILLUMInullnullE null Enull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . nullnullnull LUMInullnullE null Lnull
14、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . nullnullnull LUMInullUS EnullTnullnull null Mnull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15、 nullnullenullerences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . nullIEnull TMnullnullnullnullnullnullIEnull TMnullnullnullnullnullTnullE FInullE LInullnullTInullnullMETnullInullSEvery discipl
16、ine has its onulln special terminology and lighting is no enullception. nullortunatelynull in lightingnull there are only five basic metrics that need to be learnednull unfortunatelynull they have similar names and unusual unitsnull and may be a challenge for a beginner in lightnulling to comprehend
17、 and understand.nullor those readers nenull to lighting but not to the broader field of electromagnetic radiationnull light is defined as radiant energy that is capable of enullciting the retina and producing a visual sensation.1nullnull LUMInullnullUS FLUnullnull nullLunullinous Flunull is the time
18、 rate of flonull of light nullevalunullated in terms of nullhat the nullaveragenull human eyenullseesnullfrom a source summed over all directions. nullnless othernullnullise notednull luminous flunull is defined for photopic vision.nullThe symbol for luminous flunull is the nullreenull letter nullPh
19、inull nullnull.The nullI nullInternational nullystem of nullnitsnull unit of luminous flunull is the lunullen nulllmnull.Figure 1 illustrates the light output or luminous flunull leaving the lamp in nearly all directions.The most common analogy is fluid flunullnullnullhich is the time rate of flonul
20、l of nullaternull as shonulln in Figure 2null nullhen the garden hose valve is openednull streams of nullater emerge and travel outnullard. nullnullere it not for gravitynull the analogy nullould be completenull but the nullater streams eventually bend tonullard the ground.nullA second analogy is th
21、e electrical onenull in nullhich luminous flunull is compared to electric currentnull in amperesnull nullhich is the rate of flonull of electric charge through a nullire.A lamp consumes nullatts and produces nullor emitsnulllumensnull the measure of its success in doing this is called nullefficacynu
22、ll and is measured in lumens per nullatt. Table 1 provides the lumen output and efficacy of a fenull common lamps.2nullnull LUMInullnullUS InullTEnullSITnullnull InullLunullinous intensity is the luminous flunull per unit solid angle nullthe three dimensional enulluivalent of the traditional tnullo
23、dimensional anglenull of a light source in a given direction.The symbol for luminous intensity is the capital letter I.Figure 1nullnullLight output illustrationnullFigure 2null nullrden hosenull nullmage courtenull of iStocnullhotonullLnullMnullLUMInullnullUS FLUnull nulllunullensnullLnullMnull EFFI
24、nullnullnullnull nulllunullens per nullattnullnullnullnullnullatt Tnull linear fluorescentnull nullnullnullnull nullnullnull.nullnullnullnullnullatt nulligh Performance Tnull linear fluorescentnull nullnullnullnull nullnull.nullnullnullnullnullatt TnullnullO nullhigh outputnull linear fluorescentnul
25、l nullnullnullnull nullnull.nullnullnullnullnullnullatt ceramic metal halidenull nullnullnullnull nullnull.nullnullnullnullnullatt compact fluorescent nullnulluadnullnull nullnullnullnull nullnull.nullnullnullnullnullatt tungsten halogen nulllonull voltage reflectornull nullnullnull nullnull.nullnul
26、lnullnullnullatt incandescent nullA lampnull nullnullnull nullnull.nullTable 1: Lanull Enullicaciesnull ballast is renullired to operate these lampsnulltherefore system efficacy nullll not enullal lamp efficacy.nullIEnull TMnullnullnullnullnullThe nullI unit of luminous intensity is the candela null
27、cdnullnull technical product literature nullsuch as photometric reportsnull often refers to luminous intensity in terms of candleponuller.nulleturning to Figure 1 nullcopied herenullnull the radial arronulls indicate intensity nullcdnull in the various directionsnull in this orientation the greatest
28、 intensity is donullnnullard nullhile intennullsity drops to nullero in the upnullard direction nullbecause of its basenull.nulluminous intensity is analogous to pressure in a fluid system and voltage in an electric system.Photometric testing typically returns a nullcandela disnulltributionnull char
29、t such as the one shonulln in Table 2. The polar angles are vertical anglesnull nullith nullnull straight donulln nullnadirnull and nullnullnull horinullontal.Figures nulla and nullbnullnullillustrate the three primary vernulltical planes nullnullnullnull nullnullnullnull and nullnullnullnull of lum
30、inous intensity passing through the center of the luminaire.nullolar nullertical nulllanenullngle nullnull nullnullnull nullnullnullnull nullnullnullnull nullnullnullnull nullnullnullnullnull nullnullnullnull nullnullnullnull nullnullnullnullnullnull nullnullnullnull nullnullnullnull nullnullnullnul
31、lnullnull nullnullnullnull nullnullnullnull nullnullnullnullnullnull nullnullnullnull nullnullnullnull nullnullnullnullnullnull nullnullnullnull nullnullnullnull nullnullnullnullnullnull nullnullnullnull nullnullnullnull nullnullnullnullnullnull nullnullnullnull nullnullnullnull nullnullnullnullnull
32、null nullnullnullnull nullnullnullnull nullnullnullnullnullnull nullnullnullnull nullnullnullnull nullnullnullnullnullnull nullnullnull nullnullnull nullnullnullnullnull nullnullnull nullnullnull nullnullnullnullnull nullnullnull nullnullnull nullnullnullnullnull nullnullnull nullnullnull nullnullnu
33、llnullnull nullnullnull nullnullnull nullnullnullnullnull nullnullnull nullnullnull nullnullnullnullnull nullnullnull nullnullnull nullnullnullnullnull nullnull nullnull nullnullnullnull null null nullTable 2null Enullnullle candela distribution chartFigure nullnull nullerspective nullenullonullthe
34、sanull lunullnaireFigure nullnullrve null nullreennullindicates lunullnous intensity nullthin the vertical plane along the anulls nullonullnull null1nullnull curve null nullednullindicates lunullnous intensity nullthin the vertical plane along the anulls nullonullnullnullnull22nullnull and curve nul
35、l nullluenullindicates lunullnous intensity nullthin the vertical plane along the anulls nullonullnullnullnull2nullnullFigure nullnull nullan nullenullonulla Tnullo-Lanull Fluorescent LunullnairenullIEnull TMnullnullnullnullnullnullather than shonull the intensity profile of a lamp or luminaire as a
36、 collection of radial arronulls nulli.e. Figure 1nullnull it is more common to indicate intensity nullith a line connecting the ends of the arronulls to form intensity distribution curves as shonulln in Figure null based on the candela distribution chart shonulln in Figure 2.As luminous flunull trav
37、els outnullard from a sourcenull it ultimately impinges on surfacesnull nullhere it is reflectnullednull transmitted andnullor absorbed.The sun is a light source linulle any othernull it produces vast amounts of luminous flunull and enulltreme luminous intensity. In the photo belonullnull sunlight i
38、s transmitted through the snullylight and is absorbed bynull and reflected off the curved nullalls.The symbol for illuminance is the capital letter E.The nullI unit of illuminance is the lunull nulllnullnullnull one lunull enulluals one lumen per snulluare meter nulllmnullmnullnull. The inchnullpoun
39、d unit of illuminance is the nullootcandle nullfcnullnull one footnullcandle enulluals one lumen per snulluare foot nulllmnullftnullnull. One footcandle enulluals nullnull.nullnullnull lunullnull in most instancesnull a nullfc:nullnulllunull appronullimation is usually acceptable.nullollonulling is
40、the simplest form of the enulluation to calnullculate average illuminance nullEavgnullnull nullhere onis the luminous flunull falling on a surface nullith area A:Enulluation 1: In simplest termsnull if nullnullnull lumens fall on a desnull that is null.nullnullnullm nullnull.nullftnull by null.nulln
41、ullnullm nullnullftnullnull the average illuminullnance is The remainder of this section nullill derive the inverse snulluare lanull for calculating illuminance at a point. nullonullevernull the nullumen Methodnullnullnot the subnullect of this tenulltnull significantly enullpands Enulluation 1 to m
42、ore closenullly appronullimate average illuminance in realnullnullorld applicationsnull computer softnullare is also available that can calculate illuminance at multiple points on a surfacenull generate a single value to describe the avernullage illuminance on a large surface areanull and even produ
43、ce renderings of nullhat a space might loonull linulle.The nulley to relating the three metrics discussed thus far is the concept of the solid angle. The solid anglenulldenoted by the nullreenull letter nullomeganull nullnullnull is defined as the ratio of the intercepted surface area of a sphere ce
44、nnulltered on that point to the snulluare of the spherenulls radiusnull Figure null shonulls this relationship graphically. Thus:Enulluation 2: The remaining sections introduce the lighting metrics to nullantify amount of light falling on top of the snulllight nulllluminancenull directional luminous
45、 intensity of a lighted surface nullluminancenullnull and the amount of light reflected off the curved nullalls nulluminous enulltancenullnullnullnull ILLUMInullnullnullnullE null EnullIllunullinance on a surface is the luminous flunull density nullflunull per unit areanull incident nullfallingnull
46、on that surface. nullAnother density metric is people per snulluare mile.nullFigure null nullriunull nullmage courtenull of iStocnullhotonullFigure null Solid anglerAnullIEnull TMnullnullnullnullnullThe nullI unit of solid angle is the steradian nullsrnull.The total surface area of a sphere is 4r2nu
47、ll thereforenullthere arecontained in any sphere.nulluminous flunull nullnull and luminous intensity nullInull are directly related through solid angle by:Enulluation null: nulluminous flunull in a particular direction is the product of the intensity in that direction and the solid angle through nul
48、lhich the flunull passes.nullery fenullnull if any sources are totally uniformnull if a source of light nullere uniform nullhaving the same intensity I in all directionsnullnull thennull from Enulluations 2 and nullnull the source nullould emit I lumens in each onenullsteradian solid anglenullfor a
49、total of 4I lumens nulle.g.null a uniform point source emitting the same amount of light in all directions nullith intensity of nullnullnull candelas nullould emit nullnullnullnullnull lumensnull.Enulluation null can be used to solve for intensity as nullellnull if a nullnullnull compact fluorescent lampnull emitting nullnullnullnullnulllumensnull could be considered a uniform point sourcenullits intensity nullould bein all directions. In realitynull no light source emits light uniformly in all directionsnull so this enulluation only allonulls us to calculate the intensity of light
