lighting with artificial light

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Frdergemeinschaft Gutes Licht

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Lighting withArtificial Light


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Introduction 1

From natures light ... to artificial lighting 2 / 3

The physics of light 4 / 5

The physiology of light 6 / 7

The language of lighting technology 8 / 9

Quality features in lighting 10

Lighting level -maintained illuminance and luminance 11

Glare limitation -direct glare 12

Glare limitation -

reflected glare 13Harmonious distribution of brightness 14

Direction of light and modelling 15

Light colour 16

Colour rendering 17

Light generation by thermal radiatorsand discharge lamps 18 / 19

Overview of lamps 20 / 21

Luminaires - General requirementsand lighting characteristics 22 / 23

Luminaires - Electrical characteristics,ballasts 24 / 25

Luminaires - Operating devices, regulation, control,BUS systems 26 / 27

Review of luminaires 28 / 29

Lighting planning 30 / 31

Lighting costs 32

Measuring lighting systems 33

Lighting and the environment 34

Literature, acknowledgements for photographs.order cards 35

Imprint 36

Information from Frdergemeinschaft Gutes Licht 37

Contents


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Booklet 1 of the Information on Lighting Applicationsseries published by Frdergemeinschaft Gutes Licht isintended for all those who want to delve into the topic

of light and lighting or wish to familiarize themselves with thebasics of lighting technology. The present edition (publishedJuly 2004) is a revised version of the May 2000 edition takingaccount of all current standards.

It also forms the introduction to a series of publicationsdesigned to provide useful information on lighting applicationsfor all those involved in planning or decision-making in the fieldof lighting.

One of the objectives of the series is to promote awareness ofa medium which we generally take for granted and use withouta second thought.

It is only when we get involved in making light, in creatingartificial lighting systems, that things get more difficult, moretechnical.

Effective lighting solutions naturally call for expertise on thepart of the lighting designer. But a certain amount of basicknowledge is also required by the client, if only to facilitatediscussion on good lighting with the experts.

This publication and the other booklets in the series aredesigned to convey the key knowledge and information aboutlight, lamps and luminaires needed to meet those require-ments.

Light is not viewed in these booklets as simply a physicalphenomenon; it is considered in all its implications for humanlife. As the radiation that makes visual contact possible, light

plays a primarily physiological role in our lives by influencingour visual performance; it also has a psychological impact,however, helping to define our sense of wellbeing.

Furthermore, light has a chronobiological effect on the humanorganism. We know today that the retina of the eye has aspecial receptor which regulates such things as the sleephormone melatonin. Light thus helps set and synchronize ourbiological clock, the circadian rhythm that regulates activeand passive phases of biological activity according to the timeof day and year.

So the booklets published by Frdergemeinschaft Gutes Lichtnot only set out to provide information about the physics oflight; they also look at the physiological and psychological

impact of good lighting and provide ideas and advice on thecorrect way to harness light for different applications fromstreet lighting to lighting for industry, schools and offices, tolighting for the home.

Illustrations:01 Caf Terrace at Night (1888), Vincent Van Gogh (1853

- 1890), Rijksmuseum Krller-Mller, Otterlo, Netherlands02 The Artists Sister with a Candle (1847), Adolf Menzel

(1815 1905), Neue Pinakothek, Munich, Germany03 The Sleepwalker (1927), Ren Magritte (1898 1967),

privately owned04 Installation, Maurizio Nanucci (1992)

Light has always held a special fascination in art and architecture too. Brightnessand shadow, colour and contrast shape the mood and atmosphere of a room or space.They even help define fleeting moments.


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Light is life. The relation-ship between light andlife cannot be stated

more simply than that.

Most of the information wereceive about our surround-ings is provided by our eyes.We live in a visual world. Theeye is the most importantsense organ in the humanbody, handling around 80%of all incoming information.Without light, that wouldbe impossible light is themedium that makes visualperception possible.

From natures light ... to artificial lighting

The light of the sun, vene-rated in ancient cultures asa god, determines the pulseof life and the constant yetsubtly changing alternation ofday and night.

Insufficient light or darknessgives rise to a sense ofinsecurity. We lack informa-tion, we lose vital bearings.Artificial lighting during thehours of darkness makes usfeel safe.

So light not only enables us tosee; it also affects our moodand sense of wellbeing.

The light of the moon andstars has only 1/500,000th ofthe intensity of sunlight. Butthe sensitivity of our eyes stillenables us to see.

Lighting level and light colour,modelling and switchesfrom light to dark impact onmomentary sensations anddetermine the rhythm of ourlives.

In sunlight, for instance, illu-minance is about 100,000lux. In the shade of a tree it isaround 10,000 lux, while on a

moonlit night it is 0.2 lux, andeven less by starlight.

People nowadays spendmost of the day indoors inilluminances between 50 and500 lux. Light sets the rhythmof our biological clock but it

needs to be relatively intenseto have an effect on the cir-cadian system (> 1000 lux),

so for most of the time welive in chronobiological dark-ness. The consequencesare troubled sleep, lackof energy, irritability, evensevere depression.

As we said above, light is life.Good lighting is important forseeing the world around us.What we want to see needsto be illuminated.Good lighting also affects theway we feel, however, andthus helps shape our qualityof life.


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Around 300,000 yearsago, man began touse fire as a source of

warmth and light. The glowingflame enabled people to livein caves where the rays of thesun never penetrated.

The magnificent drawings inthe Altamira cave artworksdating back some 15,000years can only have beenexecuted in artificial light. Thelight of campfires, of kindlingtorches and oil and tallowlamps radically changed theway prehistoric man lived.

But light was not only usedin enclosed spaces. It wasalso harnessed for applica-tions outdoors. Around 260BC, the Pharos of Alexandriawas built, and evidence from378 AD suggests there were

lights in the streets of theancient city of Antioch.

Ornamental and functionalholders for the precious light-giving flame appear at a veryearly stage in the historicalrecord. But the liquid-fuellamps used for thousandsof years underwent no reallymajor improvement until AimArgands invention of the cen-tral burner in 1783.

That same year, a process

developed by Dutchman JanPieter Minckelaers enabledgas to be extracted fromcoal for streetlamps. Almostsimultaneously, experiments

For the majority of peopletoday, life without artificiallighting would be unimagi-nable.

Advances in the develop-ment of electric dischargelamps, combined with modernluminaires, has led to high-performance lighting systems.

started on electric arc lamps fuelling research whichacquired practical signifi-cance in 1866 when WernerSiemens succeeded in gener-ating electricity economicallywith the help of the dynamo.But the real dawn of the ageof electric light came in 1879,with Thomas A. Edisons re-invention and technologicalapplication of the incan-descent lamp invented 25years earlier by the Germanclock-maker Johann HeinrichGoebel.

With each new light source from campfire and kindling tocandle and electric light bulb luminaires were devel-oped to house and harnessthe new lamps. In recentdecades, lamp and luminairedevelopment has been par-

ticularly dynamic, drawingon the latest technologies,new optical systems and newmaterials while at the sametime maximising economicefficiency and minimisingenvironmental impact.

For more than 2,000 years,artificial lighting has illumi-nated the night and providedsecurity and bearings forhuman beings.


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The physics of light

Man has always beenfascinated by lightand has constantly

striven to unravel its myster-ies. History has producedvarious theories that todaystrike us as comical butwere seriously propoundedin their time. For example,since no connection could bediscerned between a flameand the object it renderedvisible, it was at one time sup-posed that visual rays wereprojected by the eyes andreflected back by the object.Of course, if this theory weretrue, we would be able to seein the dark...

In 1675, by observing theinnermost of the four largemoons of Jupiter discoveredby Galileo, O. Rmer wasable to estimate the speed of

light at 2.3 x 10

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m/s.

A more precise measure-ment was obtained using anexperimental array devisedby Lon Foucault: 2.98 x 108.The speed of light in emptyspace and in air is generallyrounded up to 3 x 108 m/s or300,000 km/s.

This means that light takesaround 1.3 seconds to travelfrom the Moon to the Earthand about 81/3 minutes to

reach the Earth from the Sun.Light takes 4.3 years to reachour planet from the fixed starAlpha in Centaurus, about2,500,000 years from theAndromeda nebula and more

than 5 billion years from themost distant spiral nebulae.

Different theories of lightenable us to describeobserved regularities andeffects.

The corpuscular or particletheory of light, according towhich units of energy (quanta)are propagated at the speedof light in a straight line fromthe light source, was pro-posed by Isaac Newton. Thewave theory of light, whichsuggests that light moves ina similar way to sound, wasput forward by ChristiaanHuygens. For more than ahundred years, scientistscould not agree which theorywas correct. Today, both con-cepts are used to explain theproperties of light: light is thevisible part of electromagneticradiation, which is made up ofoscillating quanta of energy.

It was Newton again who dis-covered that white light con-tains colours. When a narrowbeam of light is directed ontoa glass prism and the emerg-

ing rays are projected onto awhite surface, the colouredspectrum of light becomesvisible.

In a further experiment,Newton directed the colouredrays onto a second prism,from which white light onceagain appeared. This wasthe proof that white sunlightis the sum of all the coloursof the spectrum.

In 1822, Augustin Fresnelsucceeded in determiningthe wavelength of light andshowing that each spectralcolour has a specific wave-length. His statement that

light brought to light createsdarkness sums up his reali-zation that light rays of thesame wavelength canceleach other out when broughttogether in correspondingphase positions.

Max Planck expressed thequantum theory in the for-mula:

=h

The energy E of an energyquantum (of radiation) isproportional to its frequencyv, multiplied by a constant h(Plancks quantum of action).

Within the wide range ofelectromagnetic radiation,visible light constitutes onlya narrow band.

With the aid of a prism,white sunlight can be splitup into its spectral colours.

Both the particleand the wavetheory of light areused to provide asuccinct descrip-tion of the effects

of light and howthese conform tonatural laws.


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The Earths atmosphereallows visible, ultravioletand infrared radiation to

pass through in such a waythat organic life is possible.Wavelengths are measuredin nanometres (nm) =10-9 m =10-7 cm. One nanometre is aten-millionth of a centimetre.

Light is the relatively narrowband of electromagneticradiation to which the eye issensitive. The light spectrumextends from 380 nm (violet)to 780 nm (red).

Each wavelength has adistinct colour appearance,and from short-wave violetthrough blue, green, green-yellow, orange up to long-wave red, the spectrum of

sunlight exhibits a continuoussequence.Coloured objects only appearcoloured if their colours arepresent in the spectrum ofthe light source. This is thecase, for example, with thesun, incandescent lampsand fluorescent lamps withvery good colour renderingproperties.Above and below the visibleband of the radiation spec-trum lie the infrared (IR) andultraviolet (UV) ranges.The IR range encompasseswavelengths from 780 nm to

1 nm and is not visible to theeye. Only where it encoun-ters an object is the radiationabsorbed and transformedinto heat. Without this heatradiation from the sun, theEarth would be a frozenplanet. Today, thanks to solartechnology, IR radiation hasbecome important both tech-nologically and ecologically asan alternative energy source.

For life on Earth, the rightamount of radiation in the UVrange is important. This radia-tion is classed according to itsbiological impact as follows:

UV-A (315 to 380 nm),

suntan, solaria; UV-B (280 to 315 nm), ery-thema (reddening of the skin),sunburn; UV-C (100 to 280 nm),cell destruction, bactericidallamps.

Despite the positive effectsof ultraviolet radiation e.g.UV-B for vitamin D synthe-sis too much can causedamage. The ozone layer ofthe atmosphere protects us

from harmful UV radiation,particularly from UV-C. Ifthis layer becomes depleted(ozone gap), it can havenegative consequences forlife on Earth.

The prism combines thespectral colours to form whitelight. Sunlight is the combi-nation of all the colours of itsspectrum.

When the artificial light froma fluorescent lamp is split up,the individual spectral coloursare seen to be rendered toa greater or lesser extent,depending on the type oflamp.

Compared with its appea-rance in daylight, a red roselooks unnatural under the

monochromatic yellow lightof a low-pressure sodiumvapour lamp. This is becausethe spectrum of such lightcontains no red, blue or green,so those colours are notrendered.


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The optical componentsof the eye can be com-pared to a photographic

camera.

The image-producing opticsconsist of the cornea, thelens and the interveningaqueous humour. Alterationof the focal length neededfor accurate focusing onobjects at varying distancesis effected by an adjustmentof the curvature of the refrac-tive surfaces of the lens. Withage, this accommodativecapacity decreases, due to ahardening of the lens tissue.

With its variable centralopening the pupil the irisin front of the lens functionsas an adjustable diaphragmand can regulate the incidentluminous flux within a range

of 1:16. At the same time, itimproves the depth of field.The inner eye is filled with aclear, transparent mass, thevitreous humour.

The retina on the inner wallof the eye is the projectionscreen. It is lined with some130 million visual cells. Close

The physiology of light

The 7 million or so cones arethe more sensitive receptorsfor colour. These take overat higher levels of luminanceto provide day vision. Theirmaximum spectral sensitivitylies in the yellow-green rangeat 555 nm. There are threetypes of cone, each with a dif-ferent spectral sensitivity (red,green, blue), which combineto create an impression ofcolour. This is the basis ofcolour vision.

The ability of the eye to adjust

to the optical axis of the eyethere is a small depression,the fovea, in which the visualcells for day and colour visionare concentrated. This is theregion of maximum visualacuity.

Depending on the level ofbrightness (luminance), twotypes of visual cell conesand rods are involved in thevisual process.

The 120 million rods arehighly sensitive to brightnessbut relatively insensitive tocolour. They are thereforemost active at low luminancelevels (night vision); theirmaximum spectral sensitivitylies in the blue-green regionat 507 nm.

to higher or lower levels ofluminance is termed adapta-tion.

The adaptive capacity of theeye extends over a luminanceratio of 1:10 billion. Thepupils control the luminousflux entering the eyes withina range of only 1:16, whilethe parallel switching of theganglion cells enables theeye to adjust to the far widerrange. The state of adaptationaffects visual performance atany moment, so that thehigher the level of lighting,the more visual perform-ance will be improved andvisual errors minimized. Theadaptive process and henceadaptation time depend onthe luminance at the begin-ning and end of any changein brightness.

Dark adaptation takes longerthan light adaptation. The eyeneeds about 30 minutes toadjust to darkness outdoorsat night after the higher light-ing level of a workroom. Onlya few seconds are required,however, for adaptation tobrighter conditions.Sensitivity to shapes andvisual acuity are prerequisitesfor identification of details.Visual acuity depends notonly on the state of adapta-

tion but also on the resolvingpower of the retina and thequality of the optical image.

Two points can just be per-ceived as separate when

The eye is a sensory organwith extraordinary capa-bilities. Just a few highlysensitive components com-plement each other to form aremarkable visual instrument:

a corneab lensc pupild irise suspensory ligaments/

ciliary muscles

f vitreous humourg sclerah retinai blind spotk optic nerve

l fovea

Curve of relative spectralsensitivity for day vision(cones) V() and night vision(rods) V().

Schematic structure ofthe retina:1 ganglion cells2 bipolar cells3 rods4 cones


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their images on the retina aresuch that the image of eachpoint lies on its own conewith another unstimulatedcone between them.Inadequate visual acuity canbe due to eye defects, suchas short- or long-sighted-ness, insufficient contrast,insufficient illuminance.

Adaptation of the eye:On coming out of a bright roomand entering a dark one, we atfirst see nothing only aftera certain period of time doobjects start to appear out ofthe darkness.

Where two points 0.3 mmapart are identified from a dis-tance of 2 m, visual acuity is 2.If we need to be 1 m from thevisual object to make out thetwo points, visual acuity is 1.

Four minimum require-ments need to be met topermit perception andidentification:

1. A minimum luminanceis necessary to enableobjects to be seen (adapta-tion luminance). Objects thatcan be identified in detaileasily during the day become

indistinct at twilight and areno longer perceptible in dark-ness.

2. For an object to be iden-tified, there needs to be adifference between its bright-ness and the brightness ofthe immediate surroundings(minimum contrast). Usu-ally this is simultaneously a

colour contrast and a lumi-nance contrast.

3. Objects need to be of aminimum size.

4. Perception requires aminimum time. A bullet, forinstance, moves much toofast. Wheels turning slowlycan be made out in detail but

become blurred when spin-ning at higher velocities. Thechallenge for lighting technol-ogy is to create good visualconditions by drawing on ourknowledge of the physiologi-cal and optical properties ofthe eye e.g. by achievinghigh luminance and an evendistribution of luminancewithin the visual field.


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The language of lighting technology

Luminous flux is the rate at which light isemitted by a lamp. It is meas-ured in lumens (lm). Ratingsare found in lamp manufactur-ers lists.The luminous flux of a 100 Wincandescent lamp is around1380 lm, that of a 20 W com-pact fluorescent lamp withbuilt-in electronic ballastaround 1200 lm.

Luminous intensity Iis the amount of luminousflux radiating in a particulardirection. It is measured incandelas (cd).The way the luminous inten-sity of reflector lamps andluminaires is distributed isindicated by curves on agraph. These are known asintensity distribution curves(IDCs).To permit comparisonbetween different luminaires,IDCs usually show 1000 lm(= 1 klm) curves.This is indicated in the IDCby the reference cd/klm.The form of presentation isnormally a polar diagram,although xy graphs are oftenfound for floodlights.

Luminous efficacyis the luminous flux of a lampin relation to its power con-sumption. Luminous efficacyis expressed in lumens perwatt (lm/W).For example, an incandes-cent lamp produces approx.14 lm/W, a 20 W compactfluorescent lamp with built-inEB approx. 60 lm/W.

Light output ratio LBis the ratio of the radiant lumi-nous flux of a luminaire tothe luminous flux of the fittedlamp. It is measured in con-trolled operating conditions.

Glareis annoying. It can be causeddirectly by luminaires or indi-rectly by reflective surfaces.Glare depends on the lumi-nance and size of the lightsource, its position in relationto the observer and the bright-ness of the surroundings andbackground. Glare shouldbe minimized by taking careover luminaire arrangementand shielding, and taking

account of reflectance whenchoosing colours and surfacestructures for walls, ceilingand floor. Glare cannot beavoided altogether.It is especially important to

avoid direct glare in streetlighting as this affects roadsafety.

Where VDU workplaces arepresent, special precau-tions must be taken to avoidreflected glare.

Reflectance indicates the percentage ofluminous flux reflected bya surface. It is an important

factor for calculating interiorlighting.

Dark surfaces call for highilluminance, lighter surfacesrequire a lower illuminance

level to create the sameimpression of brightness.

In street lighting, the three-dimensional distribution ofthe reflected light caused bydirectional reflectance (e.g.of a worn road surface) is animportant planning factor.


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Luminance Lindicates the brightness ofan illuminated or luminoussurface as perceived by thehuman eye. It is measured inunits of luminous intensity perunit area (cd/m). For lamps,the handier unit of measure-ment cd/cm is used.

Luminance describes thephysiological effect of lighton the eye; in exterior light-ing it is an important value forplanning.

With fully diffuse reflectingsurfaces of the kind oftenfound in interiors luminancein cd/m can be calculatedfrom the illuminance E in luxand the reflectance :

Illuminance Eis measured in lux (lx) on hori-zontal and vertical planes.Illuminance indicates theamount of luminous flux froma light source falling on agiven surface.

L

Maintained illuminance Emand luminance Lmdepend on the visual task tobe performed. Illuminancevalues for interior lightingare set out in the harmonizedEuropean standard DIN EN12464-1. Illuminance andluminance values for streetlighting are stipulated in DINEN 13201-2.Sports facility lighting is cov-ered by another harmonized

European standard, DIN EN12193. Maintained valuesare the values below whichaverage values on a speci-fied surface are not allowedto fall.

Uniformityof illuminance or luminanceis another quality feature.It is expressed as the ratioof minimum to mean illumi-nance (g1 = Emin / E) or, instreet lighting, as the ratio ofminimum to mean luminance(U0 = Lmin / L ).In certain applications, theratio of minimum to maximumilluminance g2 = Emin / Emaxis important.

Maintenance factorWith increasing length of serv-ice, illuminance decreases asa result of ageing and soiling

of lamps, luminaires and roomsurfaces.

Under the harmonized Euro-pean standards, designerand operator need to agreeand record maintenance fac-tors defining the illuminanceand luminance required oninstallation to ensure thevalues which need to bemaintained.

Where this is not possible,a maintenance factor of0.67 is recommended forinteriors subject to normalageing and soiling; this maydrop as low as 0.5 for rooms

subject to special soiling.For sports facility lighting,DIN EN 12193 stipulates amaintenance factor of 0.8.Maintained value and main-tenance factor define thevalue required on installation:maintained value = value oninstallation x maintenancefactor.

L =


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Quality features in lighting

Just as the nature of occu-pational and recreationalactivities differs e.g.

reading a book, assemblingminiature electronic compo-nents, executing technicaldrawings, running colourchecks in a printing works,etc. so too do the require-ments presented by visualtasks. And those require-ments define the quality cri-teria a lighting system needsto meet.

Careful planning and execu-tion are prerequisites forgood quality artificial lighting.This is what specific qualityfeatures determine:

lighting level brightness,

glare limitation visionundisturbed by either director indirect glare,

harmonious distributionof brightness an evenbalance of luminance,

light colour the colourappearance of lamps, and incombination with

colour rendering correctrecognition and differentiationof colours and room ambi-ence,

direction of light and

modelling identificationof three-dimensional formand surface textures.

Depending on the use andappearance of a room, thesequality features can be givendifferent weightings. Theemphasis may be on:

visual performance, whichis affected by lighting leveland glare limitation,

visual comfort, which isaffected by colour renderingand harmonious brightnessdistribution,

visual ambience, which isaffected by light colour, direc-tion of light and modelling.


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Lighting level Maintained illuminance and luminance

Lighting level is influencedby illuminance and thereflective properties of

the surfaces illuminated. Itis a defining factor of visualperformance.Some examples of reflect-ance: white walls up to 85% light-coloured wood panel-ling up to 50% red bricks up to 25%.The lower the reflectanceand the more difficult thevisual task, the higher theilluminance needs to be.

Maintained illuminanceMaintained illuminance isthe value below which theaverage illuminance on theassessment plane is notallowed to fall.With increasing length of ser-vice, illuminance is reduced

owing to ageing and soilingof lamps, luminaires and roomsurfaces. To compensate for

this, a new system needs tobe designed for higher illumi-nance (value on installation).The reduction is taken into

consideration by a mainte-nance factor: maintainedilluminance = maintenancefactor x illuminance on instal-lation.

Maintenance factorThe maintenance factordepends on the maintenancecharacteristics of lamps andluminaire, the degree of expo-sure to dust and soiling in theroom or surroundings as wellas on the maintenance pro-gramme and maintenance

schedule. In most cases, notenough is known at the light-ing planning stage about the

factors that will later impacton illuminance, so where amaintenance interval of threeyears is defined, the mainte-

nance factor required is 0.67for clean rooms and as lowas 0.5 for rooms subject tospecial soiling (e.g. smokingrooms).The surface on which theilluminance is realised isnormally taken as the evalu-ation plane. Recommendedheights: 0.75 m above floorlevel for office workplaces,max. 0.1 m in circulationareas. The maintained illu-minances required for indoorworkplaces are defined in DIN

EN 12464-1 for different typesof interior, task or activity.Examples:circulation areas 100 lxoffice 500 lxoperating cavity 100,000 lx

For sports lighting, referenceplanes (at floor/ground level)and illuminance requirementsare set out for different typesof sport in the harmonizedEuropean standard DIN EN12193. Illuminance is the vari-able used for planning interior

lighting because it is easy tomeasure and fairly straightfor-ward to compute.

LuminanceDetermining luminance L(measured in cd/m) entailsmore complex planning andmeasurement.For street lighting, luminanceis an essential criterion forassessing the quality of alighting system. What motor-ists see is the light reflectedin their direction from theperceived road surface (thematerial-dependent anddirectional luminance).Since the reflectance of roadsurfaces is standardized anda single observation point hasbeen defined as standard,luminance is the variable nor-mally used for planning streetlighting.

The illumination of a streetdepends on the luminous fluxof the lamps, the intensity

distribution of the luminaires,the geometry of the lightingsystem and the reflectance ofthe road surface.The quality features of streetlighting are listed in DIN EN13201-2.

Recommended values:local service street 7.5 lxmain thoroughfare 1.5 cd/mcar park 15 lx

Reflectance of walls,floor, ceiling and workingplane recommended in DINEN 12464-1.

In street lighting, luminanceis the key quantity: road usersperceive the light reflected bythe road surface as lumi-nance.


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Glare limitation direct glare

Direct glare is caused byexcessive luminance e.g. from unsuitable

or inappropriately positionedluminaires or from unshieldedgeneral-diffuse lamps.

Glare causes discomfort(psychological glare) and canalso lead to a marked reduc-tion in visual performance(physiological glare); it shouldtherefore be limited.

The TI method in streetlightingEvery motorist is aware ofthe dangers of glare in streetlighting and its implicationsfor road safety. Effective limi-tation of physiological glareis therefore an importantrequirement for good streetlighting.

The method used to limit glarein street lighting is based onthe physiological effect ofglare and demonstrates theextent to which glare reducesthe eyes threshold of percep-tion.

In outdoor lighting, physi-

ological glare is assessed bythe TI (Threshold Increment)method.

The TI value shows in per-cent how much the visual

threshold is raised as a resultof glare. The visual thresholdis the difference in luminancerequired for an object to be

just perceptible against itsbackground.

Example:Where street lighting is glare-free, the eye adapts to theaverage luminance of theroad L. A visual object on theroadway is just perceptiblewhere its luminance contrastin relation to its surroundingsis L0 (threshold value).Where dazzling light sourcesoccur in the visual field, how-ever, diffuse light enters theeye and covers the retina likea veil. Although the averageluminance of the road remainsunchanged, this additionalveiling luminance Ls causesthe eye to adapt to a higherlevel L + Ls. An object with aluminance contrast of L0 inrelation to its surroundings isthen no longer visible.

Where glare occurs, lumi-nance contrast needs to beraised to LBL for an objectto be perceptible. On a road

of known average roadwayluminance L, the increment LBL - L0 can be used asa yardstick for the impactof glare. The percentagerise in threshold values TI

The UGR method takes account of all the luminaires in alighting system which add to the sensation of brightness aswell as the brightness of walls and ceilings; it produces aUGR index.

The UGR method in indoorlightingIn indoor lighting, psycho-logical glare is rated by thestandardized UGR (Uni-fied Glare Rating) method.This is based on a formulawhich takes account of allthe luminaires in a lightingsystem which contribute toa sensation of glare. Glare isassessed using UGR tables,which are based on the UGRformula and are available fromluminaire manufacturers.

(Threshold Increment) from L0 to LBL has beenadopted as a measure ofphysiological glare and iscalculated on the basis of thefollowing formula:

Assessment of physiological glare by the TI method: lumi-nance contrast L as a function of adaptation luminance L.Where glare occurs, the luminance contrast needs to be raisedto L BL for the visual object to be perceptible.

UGR = 8 log0,25

L2

Lb p2

TI=

LBL - L0. 100

% Lo

Shielding against glareTo avoid glare due to bright light sources, lamps should beshielded. The minimum shielding angles set out below need tobe observed for the lamp luminance values stated.

Lamp luminance cd/m2 Minimum shielding angle

20,000 to < 50,000 1550,000 to < 500,000 20

500,000 30


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Glare limitation

reflected glare

Reflected glare refersto the disturbingreflections of lamps,

luminaires or bright windowsfound on reflective or glossysurfaces such as art paper,computer monitors or wetasphalt roads.

Reflected glare can be limitedby the right choice and appro-priate arrangement of lampsand luminaires.Reflected glare causes thesame kind of disturbance asdirect glare and, above all,reduces the contrasts neededfor trouble-free vision.

Reflected glare on shinyhorizontal surfaces (readingmatter and writing paper) is

assessed using the contrastrendering factor CRF, whichcan be calculated by specialsoftware. For normal officework, a minimum CRF of 0.7is enough; only work involvinghigh-gloss materials calls fora higher factor.

Reflected glare on VDUscreens is the most commoncause of complaint. It is effec-tively avoided where monitorsare arranged in such a waythat bright surfaces suchas windows, luminaires andlight-coloured walls cannot bereflected on screens. Wheresuch an arrangement is notpossible, the luminance of thesurfaces reflected on screensneeds to be reduced.

For luminaires, luminancelimits have been defined (seetable below). These dependon the anti-glare system ofthe computer monitor andapply to all emission anglesabove 65 to the vertical allaround the vertical axis.

Reflected glare, causedby veiling reflections on thesurface of the object beingviewed, is disturbing andthus makes for poor visualconditions.

Depending on the class of VDU, the mean luminance of lumi-naires which could cast reflections onto the screen needs tobe limited to 200 cd/m or 1000 cd/m above the critical beamangle of = 65 (at 15 intervals all round the vertical axis).

Reflections on monitors areparticularly annoying. Wheredirect luminaires could castreflections onto screens, theirluminance needs to be limited.

VDUs mean luminance ofluminaires and surfaces

which reflect on screens

Positive display VDUs

1000 cd/m2Negative display VDUs withhigh-grade anti-reflective systemEvidence of test certificate required

Negative display VDUs withlower-grade anti-reflective system

200 cd/m2


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Harmonious distribution of brightness

Marked differences inluminance in the fieldof vision impair visual

performance and causediscomfort, so they need tobe avoided. This applies asmuch outdoors, e.g. in sportsfacilities or street lighting, as itdoes in interior lighting.

The luminance of a desktop,for example, should be noless than one third of theluminance of the document.The same ratio is recom-mended between the lumi-nance of the work surfaceand that of other areas fur-ther away in the room. Theratio of visual task luminanceto the luminance of large sur-faces further away should notexceed 10:1.

Where luminance contrastsare not sufficiently marked,a monotonous impression iscreated. This is also foundunappealing.

On the roads, good even localluminance distribution is animportant safety requirement.It permits timely identificationof obstacles and hazards.

Harmonious distribution ofbrightness, e.g. in offices,can be achieved by lightinggeared to the colours andsurface finishes of office fur-

nishings. Factors which helpcreate a balanced distributionof luminance in the field ofvision include:

room-related or task arealighting

use of lighting with an indi-rect component for betteruniformity.

a ratio of minimum to meanilluminance (Emin/E) of atleast 0.7

adequately high wall, floorand ceiling reflectance.

A pedestrian precinctshould also be lit evenly forsafety, which need not meanthat it becomes boring.

Illuminance in a room says nothing about the harmoniousdistribution of brightness. This can be established only bydetermining the luminance of the surfaces (cd/m) indicated inthis illustration.

Indoors, harmoniousdistribution of brightness isimportant for visual comfort.On roads, safety is improvedby good longitudinal unifor-mity which correspondsto harmonious brightnessdistribution.


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59 60

Direction of light and modelling

Without light we cannotmake out objects,without shadow

we see objects only as two-dimensional images. It takesdirectional lighting and model-ling to permit 3D projection, togive objects depth.

A bright room with nothingbut diffuse lighting and noshadows makes a monoto-nous impression; the lack oforientation, poor definition ofobjects and difficulty in gaug-ing distances make us feeluncomfortable.

In contrast, point-like lightsources with extremely direc-tional beams produce hard-edged shadows. Such harshshadow renders virtuallyeverything unrecognizable;it can even cause potentially

dangerous optical illusions,e.g. where tools are used,machines are operated orstairs need to be negotiated.

Direction of light and model-ling also help define visualambience. A good ratio ofdiffuse light (e.g. from indi-rect lighting components) todirectional light (e.g. fromdirect louver luminaires ordownlights) makes for agree-able modelling.

Direction of light is generallydefined by daylight entering

Most people prefer lightto fall predominantly fromabove and the left, since thisprevents disturbing shadowsbeing cast on written work.

Light and shadow bringout the details of this whitemarble statue.

Only under directional lightfrom the side can the three-dimensional structure of thewall surface be perceived;in diffuse light it appearssmooth.

To avoid harsh shadows,floodlights are arranged sothat each individual beam eli-minates the shadow createdby others.

the room through a windowfrom a particular direction.Excessively deep shadow-ing, e.g. in front of a writinghand, can be offset by artifi-cial lighting.

In offices where desk arrange-ments are geared to incidentdaylight, it is advisable tocontrol daylight incidenceby means of window blindsand to use continuous rowsof luminaires on separateswitching circuits to lightendisturbing shadows.

Where luminaires arearranged parallel to thewindow wall, the rear row ofluminaires can lighten anydark shadows that mightoccur during the day. As day-light fades, the front row ofluminaires near the windowscan be partially or fully acti-vated to make up for the lossof natural light.

For certain visual tasks, e.g.for appraising surface charac-teristics, marked modelling bydirectional light is required.

In fast ball games such astennis or squash, adequatemodelling is necessary forfast identification of the ball,its flight path and the placewhere it will land.


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Light colour

We experience our sur-roundings not just asbrightness and dark-

ness, light and shadow, butalso in colour.

The light colour of a lamp isexpressed in terms of colourtemperature Tc measured indegrees Kelvin (K).The Kelvin temperaturescale begins at absolute zero(0 Kelvin -273C).Colour temperature is usedto denote the colour of a lightsource by comparison withthe colour of a standardizedblack body radiator.A black body radiator is anidealised solid body, e.g.made of platinum, whichabsorbs all the light that hits itand thus has a reflective radi-ance of zero.

When a black body is slowlyheated, it passes throughgraduations of colour fromdark red, red, orange, yellow,white to light blue. The higherthe temperature, the whiterthe colour.

The temperature in K at

which a black body radiatoris the same colour as thelight source being measuredis known as the correlatedcolour temperature of thatlight source. An incandescent

lamp with its warm white light,for example, has a correlatedcolour temperature of 2800 K,a neutral white fluorescentlamp 4000 K and a daylightfluorescent lamp 6000 K.For reasons of standardi-zation, the light colours oflamps are divided into threegroups: dw daylight white,nw neutral white and ww warm white.

Light colour of lamps:

Colour temperatureLight colour in Kelvin

warm white < 3300

neutral white 3300 - 5300

daylight white > 5300

Lamps with the same lightcolour can emit light of com-pletely different spectral com-position and thus with quitedifferent colour renderingproperties. It is not possibleto draw conclusions aboutcolour rendering from lightcolour.

The International Commis-sion on Illumination CIE hasdevised a triangle in which thecolours of light sources andbody colours can be classi-fied. Depending on brightness,

achromatic light (i.e. white,grey or black) is found at x = y= 0.333.All the other colours arelocated around this point.

Along the straight line from theachromatic position to the lim-iting curve (which representsthe spectral colours of sunlight)lie the colours of the same huebut differing degrees of satu-ration. Saturation increasestowards the limiting curve.The colour triangle containsall real colours. The curvedescribes the colours of theblack body radiator for thegiven temperatures (in Kelvin).

Fluorescent lamps have aline or band spectrum. Theexamples here show the spec-tra of fluorescent lamps ineach of the three groups dw,nw and ww.

In contrast, the incan-descent lamp at the bottomexhibits a continuous spec-trum.

Light colour dw daylight white

Light colour ww warm white

Light colour nw neutral white

Numeral Ra range Light colour Colourtemperature

1st numeral 2nd+ 3rd numeral in Kelvin

9 90 - 100 27 2700 K

8 80 - 89 30 3000 K

7 70 - 79 40 4000 K

6 60 - 69 50 5000 K

5 50 - 59 60 6000 K

4 40 - 49 65 6500 K

The international colourdesignation code for lampsconsists of three numerals.The first numeral indicatescolour rendering (Ra range),the second and third colourtemperature (in Kelvin).

The way we see coloursdepends not only on the light

colour and colour renderingproperties of the lamp. Wherelight colour departs from thedaylight norm, stored visualstandards enable us withincertain limits to make sub-conscious colour corrections.


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Despite identical light colour, different colour renderingproperties lead to variations in colour perception. For instance,where the spectrum of a lamp contains little red light (right), redsurface colours are only incompletely rendered.

Colour rendering

Light and colour create theatmosphere of a room andinfluence our mood and senseof wellbeing by their warmthor coldness.

Guaranteeing correct colourperception under artificial lightforms a very important part ofthe lighting designers brief.The appearance of colouredobjects is affected by theinteraction between the colour i.e. the spectral reflectance of the objects we see andthe spectral composition ofthe light illuminating them.

In everyday life, we comeacross surface colours whichcan differ in appearancedepending on how they areilluminated but which werecognize for what they arethanks to stored visual stan-dards that are independentof lighting.

For example, we have astored impression of thecolour of human skin in day-light. Where artificial lightinglacks a particular spectralcolour or exaggerates certain

colours in its spectrum (as isthe case with incandescentlamps), skin seen under itmay appear a different colourbut will still look naturalbecause of empirical compen-

sation. For coloured materialsfor which no empirical stand-ards exist, however, colourperception can vary widely.

The effect a light source hason the appearance of col-oured objects is described byits colour rendering proper-ties. These are grouped intogrades based on the generalcolour rendering index Ra.The colour rendering indexindicates how closely thecolour of an object matchesits appearance under therelevant light source.

To determine the Ra valuesof light sources, eight definedtest colours commonly foundin the environment are eachilluminated under the refer-ence light source (Ra = 100)and then under the sourcebeing evaluated. The greaterthe difference in the appear-ance of the test colours ren-dered, the poorer the colourrendering properties of thelight source under examina-tion. Under a light sourcewith an Ra = 100 rating, allthe colours have the same

optimal appearance asunder the reference lightsource. The lower the Raindex, the poorer the render-ing of the surface colours ofthe illuminated objects.

Electric lamps are classedaccording to light colour (dw,nw or ww) and colour render-ing index Ra (from 20 to 100).


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Light generation by thermal radiators

and discharge lamps

In general, lamps generatelight either by thermal radi-ation or by gas discharge,

the radiation of which is eitherdirectly visible or is made vis-ible by luminescent material.

Incandescent lampsThe incandescent lamp is athermal radiator which gener-ates light by resistance heat-ing. It consists of a tungstenfilament in a glass bulb which,depending on the model, iseither evacuated or filled withnitrogen or inert gas (argon).

The inert gas raises thetemperature of the tungstenfilament and reduces vola-tilization. This increases theluminous efficacy and, byhindering the blackening ofthe inside of the glass bulb,counteracts the decline in

luminous flux.

The luminous efficacy can befurther improved by doublingthe coiling of the resistancewire.

The mean service life of anincandescent lamp is definedas the length of serviceof 50% of all lamps undernormal working conditions.For general-service tungstenfilament lamps this is 1,000 h.

The service life and the lumi-nous flux of an incandescentlamp are influenced by thelevel of the supply voltage.

Tungsten halogen lampsA further development of theincandescent bulb is the tung-sten halogen lamp, in whichthe bulb is filled with halo-gen gas. This ensures thatvolatizing tungsten atoms arere-deposited on the coil aftera circulating process andthereby prevents blackeningof the bulb.

The main advantages oftungsten-halogen lamps areincreased luminous efficacyup to around 25 lm/W, alonger service life, e.g. 2000hours, constant luminous flux,white light colour and smalldimensions.

A distinction is made betweenthe tungsten halogen bulbs inhigh-voltage lamps for 230 Voperation and those for low-

voltage operation on 6, 12or 24 V.

Halogen reflector lamps witha metal or specular glassreflector deliver focusedbeams of light with variousbeam spreads.

In cool-beam reflector lamps2/3 of the heat (IR radiation)is diverted backwards throughthe infrared-permeablespecular surface and therebyremoved from the light beam.

Museum exhibits, for exam-ple, are thus protected fromexcessive heat.

Discharge lampsDischarge lamps generatelight by electric dischargethrough ionized gas or metalvapour. Depending on thetype of gas in the dischargetube, visible light is eitheremitted directly or UV radia-tion is converted into visiblelight by luminescent materialson the inside of the tube.

A distinction is made betweenlow- and high-pressure lamps,depending on the operatingpressure in the tube.

To operate, fluorescent lampsrequire a ballast, which servesmainly to limit the amount ofcurrent flowing through thelamp. To ignite a dischargelamp, a starter or igniter isrequired. This supplies volt-age and energy pulses high

enough to ionize the gascolumn (discharge path) andthereby ignite the lamp.

The bulbs of thefirst incandescentlamps were evacu-ated, i.e. the tung-sten wire of thefilament glowed

in a vacuum.Tungsten particlesvolatilizing off thefilament settled onthe inside of thebulb and made itincreasingly dark.The inert gas usedto fill bulbs todaylimits the freedomof movement of thetungsten mol-ecules and therebyreduces the dark-ening effect.

Tungsten Insert gas

Continuous developmentand modern manufacturingtechniques have led to new,extremely compact lampssuch as low-voltage halogencool-beam specular reflectorlamps.

1 Glass2 Cool-beam facet reflector3 High-performance burner4 Base

Electronic ballastsWhere electronic ballasts(EBs) are used, luminousefficacy and lamp life areincreased. Lamps also startinstantly and without flickeringand provide constant, steadylighting with no stroboscopiceffects. Defective lamps areautomatically shut down.

Fluorescent lamps and com-pact fluorescent lamps oper-ated by appropriate EBs canbe dimmer-controlled.

The service life of dischargelamps is generally referredto as the economic life. Thistakes account of the lamps ina lighting system which arerendered defective e.g. by abroken filament as well as thedecrease in luminous flux dueto fatigue in the fluorescentmaterial and deterioration ofthe discharge mechanism.The system luminous flux thus

defined must not fall below acertain minimum (80% ofoutput on installation).


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Fluorescent lampsThree-band fluorescent lampshave three or five especiallyprominent spectral areas inthe blue, green and red sec-tors, which make for goodcolour rendering properties.

The luminescent coating onthe inside of the lamp tubeconverts the largely invis-ible UV radiation of the gasdischarge into visible light.The chemical compositionof the luminescent materialdetermines, among otherthings, the light colour andcolour rendering propertiesof the lamp.

26 mm-diameter three-bandfluorescent lamps have a highluminous efficacy rating and

a long service life. As withall other types of fluorescentlamp, the amount of luminousflux they emit depends onthe ambient temperature: at20C, for example, it fallsbelow 20% capacity, at +60Cbelow 80%.

Three-band fluorescentlamps with a 16 mm-diameterand shorter tube have evenhigher luminous efficacy rat-ings. These T5 fluorescentlamps can only be operatedby electronic ballasts (EBS).

Two type series are available:high luminous efficacy lampsin 14 W to 35 W power ratingsfor maximum economy, andhigh luminous flux lamps in24 W to 80 W ratings for indi-

rect or direct lighting in roomswith very high ceilings. 7 mm-diameter fluorescent lampswith 6 W to 13 W ratings areused in display, furniture andpicture lights.

Induction lampsInduction lamps have no elec-trodes. The electron flow hereis induced by a magnetic field.Because induction lampshave no components whichare subject to wear, theyattain an average service lifeof 60,000 operating hours.Induction lamps are availablein spherical and as high-performance fluorescentlamps flat designs.

LEDsIn an LED, a solid-state crys-tal is induced to emit light bypassing an electric currentthrough it. The type of crys-tals used have two sectionsor regions: a region with a

Fluorescent lamps workwith mercury vapour underlow pressure. When currentflows, electrons are emittedfrom both tungsten wire elec-trodes. On their way through

the discharge tube, they col-lide with the mercury atoms.In this collision, a mercuryelectron is deflected from itspath and orbits at a greaterdistance from the nucleus.As it springs back into itsoriginal orbit, it releases thecollision energy in the formof UV radiation, which is thentransformed into visible lightby the fluorescent coating onthe inside of the dischargetube. The light colour andcolour rendering of fluores-cent bulbs can be varied overa wide range by the chemicalcomposition of the coating.

As burning time increases, the luminous flux of fluorescentlamps diminishes and individual lamps fail. These factors deter-mine the system luminous flux, which must not fall below 80%of the luminous flux on installation.

High-pressure dischargelamps possess a burner inwhich light is generated byelectrical discharge in a gas,a metal vapour or a mixtureof the two. The metal halidelamp shown above has atransparent ceramic burner,which ensures uniform colourcharacteristics throughoutthe life of the lamp.

surplus of electrons (n-typesemiconductor) and a sectionwith a deficit of electrons (p-type semiconductor). Whena direct voltage is applied,electrons flow across the

junction between the tworegions, generating light inthe process.

The light thus created has anarrow-band emission spec-trum which differs accordingto the semiconductor mate-rial used. White LEDs canbe created by additive colourmixing or by luminescenceconversion. Their colourtemperatures are between4,000 and 7,000 Kelvin andcolour rendering index Raaround 70.

Among the most importantadvantages of LEDs are theirsmall dimensions, long lifeand low failure rates. Also,they emit no IR or UV radia-tion.

LEDs are only three to fivemillimetres high and thuspermit totally new luminairedesigns.


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5 6

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12

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Lamps

Light colour: ww = warm white, nw = neutral white, dw = daylight white 1) for EB operation only 2) luminous flux at 35C

No. Lamp type Power rating Luminous flux Luminous flux Light colour(Watts) (lumens) (lumens/Watt)

Linear three-band fluorescent lamps

1

T5; 16 mm dia.1)14 - 35 1250 - 36502) 89 - 104 ww,nw,dw

high luminous efficacy

2T5; 16 mm dia.1)

24 - 80 1850 - 70002) 77 - 88 ww,nw,dwhigh luminous flux

3 T8; 26 mm dia. 18 - 58 1350 - 5200 75 - 903) ww,nw,dwCompact fluorescent lamps

4 2-, 4-, 6-tube lamp 5 - 120 250 - 9000 50 - 75 ww,nw5 2-tube lamp 18 - 80 1200 - 6000 67 - 75 ww,nw,dw6 4-tube lamp 18 - 36 1100 - 2800 61 - 78 ww,nw

2D-lamp 10 - 55 650 - 3900 65 - 71 ww,nw,dwEnergy-saving lamps

7 Incandescent shape 5 - 23 150 - 1350 30 - 59 ww8 standard shape 5 - 23 240 - 1500 48 - 65 ww

230 V tungsten halogen lamps

9 with jacket 25 - 250 260 - 4300 10 - 17 ww10 miniature 25 - 75 260 - 1100 10 - 15 ww11 with reflektor 40 - 100 ww12 with base at both ends 60 - 2000 840 - 44000 14 - 22 wwLow voltage 12 V halogen lamps

13 with reflektor 20 - 50 ww14 pin-based lamps 5 - 100 60 - 2300 12 - 23 wwMetal-halide lamps

15 with base at one end 35 - 150 3300 - 14000 85 - 95 ww,nw16 with base at both ends 70 - 400 6500 - 36000 77 - 92 ww,nw

High-pressure sodium vapour lamps 17 tubular 35 - 1000 1800 - 130000 51 - 130 wwLow-pressure sodium vapour lamps

18 tubular 18 - 180 1800 - 32000 100 - 178 yellowLight emitting diodes19 LED 0,7 - 1,5 18 - 27 13 - 23

9

10


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Good lighting depends on theright choice of lamp. Beloware the most important lamptypes and their specifica-tions.

Three-band fluorescentlamps (1, 2, 3)Three-band fluorescent lampsoffer high luminous efficacycoupled with good colourrendering and a long servicelife. Operated by electronicballasts (EBs), they achievean even higher luminous effi-cacy and longer service life.16 mm-diameter T5 lampsare designed for EB operationonly. With appropriate EBs,all three-band fluorescentluminaires can be dimmer-controlled.

Compact fluorescent lamps(4, 5, 6)Compact fluorescent lampshave the same characteris-tics as three-band fluorescentlamps. Here too, luminousefficacy, service life and light-ing comfort are enhancedby electronic ballasts anddimmer control is possible

with appropriate EBs.

Energy-saving lamps (7, 8)Energy-saving lamps have abuilt-in ballast and a screwbase (E14 or E27). They con-sume as much as 80% lesspower and have a consider-ably longer life than incandes-cent lamps.

230 V tungsten halogenlamps (9, 10, 11, 12)Tungsten halogen lamps forline operation produce an

agreeable white light withgood colour rendering prop-erties. They have a longerservice life than incandescentlamps and achieve higherluminous efficacy. They arefully dimmable and availablealso as reflector lamps.

Low-voltage 12 V halogenlamps (13, 14)Low-voltage halogen lampsproduce an agreeable whitelight with very good colourrendering properties. To

operate them, a transformeris needed to reduce the volt-age to 12 V. With appropriatetransformers, they can bedimmer-controlled.IRC (Infra-Red Coating) lampsconsume 30% less power forthe same luminous flux.

Metal halide lamps (15, 16)These lamps are noted fortheir high luminous efficacyand excellent colour render-ing properties. Modern metalhalide lamps have a ceramicburner, which produces lightof a constant colour through-out the lamps life. A ballastis needed to operate metalhalide lamps. EB operationmakes for a longer lamplife and enhanced lightingcomfort.

High-pressure sodiumvapour lamps (17)Very high luminous efficacyand long lamp life makehigh-pressure sodium vapourlamps a highly economicaloption for outdoor lighting.They consume only half asmuch power as high-pres-sure mercury vapour lamps.

Appropriate ballasts andigniters are needed to oper-ate high-pressure sodiumvapour lamps.

Low-pressure sodiumvapour lamps (18)This type of lamp is notedfor having a higher luminousefficacy than any other.Because of its monochro-matic beam, it is particularlygood at penetrating fog andmist. Low-pressure sodiumvapour lamps are used for

illuminating port and lockcontrol installations and forsecurity lighting.

Light-emitting diodes (19)LEDs come in numerousshapes and colours. They areextremely small, have a highresistance to impact and avery long service life and emitneither IR nor UV radiation.Given a special fluorescentcoating, LEDs produce whitelight. LEDs are designed ford.c. operation.

) luminous efficacy increases to 81 - 100 lm/W with EB operation

Colour rendering Baseindex

80 to 89 G5

80 to 89 G5

80 to 89 G13

80 to 89 G23, G24, GX24, 2G7/880 to 89 2G1180 to 89 2G1080 to 89 GR8, GR10, GRY10

80 to 89 E14, E2780 to 89 E14, E27

90 and higher E14, E2790 and higher G990 and higher E14, E27, GZ10, GU1090 and higher R7s

90 and higher GU5,390 and higher G4, GY6,35

80 to 89, 90 and higher G12, G8,580 to 89, 90 and higher RX7s, Fc2

20 to 39 E27, E40

BY22d

17 18

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Luminaires

General requirements and lighting characteristics

Selection of luminairesLuminaires are selected on the basis of: application

interior or exterior luminaire, type and number of lamps

incandescent lamp, low-pressure or high-pressure dischargelamp,

structural typeopen or closed luminaire,

type of mountingrecessed, surface-mounted or pendant luminaire,

lighting characteristicssuch as luminous flux distribution, luminous intensity distri-bution, luminance distribution and light output ratio,

electrical characteristics, including components requiredfor lamp operation electrical reliability, protection class, radio interference

suppression, ballast, igniter/starter, etc., mechanical characteristics

mechanical reliability, degree of protection, fire safetyfeatures, impact resistance, material properties, etc.,

size, construction and design.

Luminous flux distribution

Total luminous flux L is thesum of the partial luminousflux emitted in the lower half

U and upper half

O of theluminaire. Luminaires arecategorized by the amount oflower luminous flux they emitand assigned to groups A toE as defined in DIN 5040.

For most outdoor applica-tions, luminaires for directlighting are normally thepreferred option. However,for decorative lighting inpedestrian precincts, parksetc., luminaires with a smallindirect lighting componentcan be usefully employedto highlight trees or buildingfaades.

CAD systems are used forluminaire development.

Lighting materialsIn order to direct, distributeor filter the luminous flux oflamps, two basic kinds oflighting materials are used: reflective materials translucent light-transmitting

materials.Reflective materials are usedto reflect as much light aspossible. They can be subdi-vided into materials for:

directional reflectione.g. specular reflectors andlouvers of highly polishedanodised aluminium; coupledwith precise specular design,these optical controllers makefor finely defined beams andluminance control.

mixed reflectione.g. satinized specular lou-vers; in contrast to matt mate-rials, the surface of theseoptical controllers has a morepronounced directional com-ponent for defined shieldingconditions.

diffuse reflectione.g. matt specular louversor reflectors and louverswith enamelled surfaces;the luminaire face is clearlyvisible owing to its higherluminance.


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Luminous intensitydistributionThe three-dimensional distri-bution of the luminous inten-sity of a luminaire is indicatedby the luminous intensitydistribution model. It can beshown for various planes inpolar diagrams (IDCs). Tofacilitate comparison, theintensities relate to 1000 lmof the lamps in the luminaireand are expressed accord-ingly as cd/klm (candelas perkilolumen).

The shape of an IDC showswhether the luminaire has anarrow- or wide-angle,symmetrical or asymmetricalbeam.

Intensity distribution curvesare usually establishedunder standardized luminaireoperating conditions usinga computer-controlled rotat-ing mirror goniophotometer.They provide the basis forplanning interior and exteriorlighting.

Computer-generated three-dimensional intensity distribu-tion of an exterior luminaire.

Luminance distribution andshieldingTo assess the glare pro-duced by interior luminaires,it is necessary to know theirmean luminance at anglescritical for glare.Mean luminance is the quo-tient of luminous intensityand the effective luminousarea perceived by observers.

In street lighting, glaredepends, among otherthings, on the size of theluminous area and the lightemitted by the luminaires.Luminous intensity at criticalbeam angles is limited bydeflection within the opticalcontrol system.

Computer-calculatedreflector/louver combinationsare used to achieve optimalluminance distribution witheffective luminaire shielding.

Directionally translucent

materials(such as glass and plastics)are also employed for opticalcontrol by harnessing theircapacities for refracting andreflecting light. When a beamof light passes from one opti-

cal medium into another, itchanges direction accordingto the angle of incidenceand thus undergoes opticalcontrol.

Light output ratio LBThis is an important quantityfor assessing the energy effi-ciency of a luminaire and itslighting performance. Lightoutput ratio LB is the ratio ofthe luminous flux radiated bya luminaire to the sum of theluminous fluxes of its lamps,measured under specificoperating conditions.

Those conditions define thenormal operating position ofthe luminaire and a normalambient temperature of

25C.

Although a track-mountedgeneral-diffuse luminairehas a higher light output ratioLB than a shielded specu-lar luminaire, it also causesmore glare. Specular louverluminaires, for instance,produce substantially higherilluminance on the workingplane. Light output ratio isthus not a reliable yardstickfor illuminance on the work-ing plane.


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Luminaires

Electrical characteristics, ballasts

Class of protectionLuminaires are divided intothree classes of protectionaccording to the protectivemeasures taken against elec-tric shock:

Class I: Touch-accessiblemetal components are con-nected to the protective

conductor. The protectiveconductor terminal is indi-cated by the symbol

Class II: Live componentsare provided with additionalprotective insulation. Connec-tion to the protective conduc-tor is not allowed.Symbol

Class III: Luminaires areoperated on protective extra-low voltages (< 42 V) thatpresent no danger to human

beings.Symbol

Luminaires need to be desi-gned for conformity with oneof the three electrical classesof protection against electricshock.

IP 20 IP 20

IP 65

IP 40

IP 54 IP 54

Degrees of protection IPThe mechanical design ofluminaires must be such thatthey are adequately protectedagainst the ingress of foreignbodies and moisture. Thedegree of protection is indi-cated by the IP (Ingress Pro-tection) numbering system

The first numeral indicates thedegree of protection againstforeign bodies, the secondnumeral protection againstwater.

An IP 20 luminaire, for exam-ple, is protected against theingress of foreign bodies> 12 mm, but not againstmoisture. A luminairedesigned for use in dampinteriors, with a degree of pro-tection of IP 65, is protectedagainst the ingress of dust

and against jets of water.

The luminaires are examples of different IP degrees of pro-tection and show that the higher degrees of protection requiremuch more sophisticated mechanical solutions.

Degree of 1st numeral 2nd numeralprotection foreign body protection water protection

IP 11 foreign bodies > 50 mm drops of waterIP 20 foreign bodies > 12 mm unprotected

IP 23 foreign bodies > 12 mm spraywater

IP 33 foreign bodies > 2,5 mm spraywaterIP 40 foreign bodies > 1 mm unprotected

IP 44 foreign bodies > 1 mm splashwater

IP 50 dust-protected unprotected

IP 54 dust-protected splashwater

IP 65 dustproof jetwater

IP 66 dustproof floodwater

Electromagnetic compa-tibilityElectrical equipment andelectronic circuits can sendout intended or unintendedhigh-frequency electromag-netic signals, which are eitherbeamed through the air orfed into cables. Such equip-ment is also susceptible toexternal interference whichcan prevent it from operat-ing normally. Growing use ofelectronic equipment makesit vital to ensure that thiskind of cross-interference issuppressed. Luminaires fordischarge lamps are potentialsources of such interference.

Under Ordinance 242/1991issued by the Federal Min-

ister for Post and Telecom-munications on 11 December1991, luminaires licensed foruse in Germany are requiredto meet certain standards ofimmunity to interference andinterference suppression.The ordinance is based onthe Electromagnetic Compat-ibility Act incorporating ECDirective 89/336/EEC Elec-tromagnetic Compatibilityinto German law.

Compliance with the relevantstandards is evidenced by theEMZ symbol of the VDE testand certification institute.


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Energy efficiency of lumi-nairesMost of the electrical energyconsumed is consumed bythe lamp and its operatinggear. To indicate the energyconsumption of the ballast/lamp system, an energyclassification system hasbeen introduced at Europeanlevel (Directive 2000/55/ECon energy efficiency require-ments for ballasts for fluores-cent lamps).

The EEI (Energy EfficiencyIndex) distinguishes betweenseven classes of ballast:A1 Dimmable electronic

ballasts (EBs)A2 Electronic ballasts (EBs)

with reduced lossesA3 Electronic ballasts (EBs)B1 Magnetic ballasts with

very low losses (LLBs)

B2 Magnetic ballasts withlow losses (LLBs)C Magnetic ballasts with

moderate losses (CBs)D Magnetic ballasts with very

high losses (CBs).

The sale of Class D ballastshas been prohibited since 21May 2002; Class C ballastsmust be withdrawn from themarket by 21 November 2005at the latest.

Other symbols onluminaires

Impact-resistant to VDE,Not for tennis if openings> 60mmProtected againstexplosion

Max. permissible ambienttemperature, deviatingfrom 25C

Non-permissible lamps

Min. clearance fromilluminated surface

Fire safetyWhen selecting luminaires,consideration should be givento the fire-resistance of themounting surfaces and theluminaire surroundingsDIN VDE 0100 Part 559t pu ates t at um na res w the symbol are suitable fordirect installation on buildingmaterials that remain dimen-sionally stable and stationaryat temperatures up to 180 C.Luminaires without a fireprotection symbol may onlybe directly installed on non-flammable building materialssuch as concrete.

At locations exposed to firehazards, however, wherehighly flammable materialssuch as textile fibres etc. maybe deposited on luminaires,nly models with the ymbol

may be installed. Such lumi-naires are designed so thetemperature of their surfacesdoes not rise above the stipu-lated threshold temperature.Luminaires for direct mount-ing in or on furnishings,e.g. furniture, must bear the

or sym o , epen ngn the material of the mount-

ing surface.

BallastsOne thing all discharge lampshave in common is their nega-tive current/voltage charac-teristic: a current supplied atconstant voltage reaches anintensity that would destroythe lamp. Hence the needfor discharge lamps to beoperated by ballasts. Theseserve to limit the current and,in combination with e.g. start-ers, to ignite the lamps

Growing energy awarenesshas prompted major tech-nological improvements inballasts, especially ballastsfor fluorescent lamps. Theconventional ballast (CB) hasnow been superseded by the(inductive) low-loss ballast.(LLB) and the electronic bal-last (EB).

Electronic ballasts convert230 V/50 Hz line voltage intoa high-frequency a.c. voltageof 25 to 40 kHz, which lowersthe power intake of a 58 Wlamp to around 50 W whilemaintaining virtually identicalluminous flux. The powerrequired by a lamp/EB systemin our example is reduced to55 W, which represents a23% saving in comparisonwith the CB system. Useof efficient, energy-savingballasts is encouraged by

measures taken by the EU.Even today, more than 40%of new and refurbished light-ing systems with fluorescent including compact fluores-cent lamps are already fittedwith EBs.

In addition to the considerableenergy savings achieved,making for short EB pay-backtimes of only a few years,high-frequency EB operationof fluorescent lamps and agrowing number of other dis-charge lamps by EB has otheradvantages:

Advantages of electronicballasts EB

low ballast losses higher lamp luminousefficacy

optimal transformation ofwattage into light

reduced operating costs reduced air-conditioningcosts

no starter, no p.f. correctioncapacitor

can be run on a.c. or d.c.current

constant lamp performanceover wide voltage range

suitable for emergencylighting

low magnetic inductioninterference

use in medical examinationrooms

defective lamps automati-cally shut down (fire protec-tion)

approx. 50% longer lamplife

enhanced lighting comfortand quality

dimmer control possible(special EB)

Impact resistanceLuminaires for use in sportsfacilities in which ball games

are played must be impact-re-sistant and be marked withthe symbol indicating suit-ability for sports facility use.This also applies to luminaireaccessories and mountingcomponents

Luminaire fire protectionsymbols

Luminaires for mountingon building partsnon-flammable up to 180C.

As F symbol, but suitablefor use with thermalinsulation backing.

Luminaires for mountingin/on furniture where themounting surface is non-flammable up to 180C.

furniture where the

Luminaires for locationsexposed to fire hazards.Temperature of horizontalluminaire surfaces max.90C in normal operation.Glass surfaces of fluorescentlamps max. 150C.

> Observemountinginstructiuons

> Observemountinginstructiuons


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Luminaires

Operating devices, regulation, control, BUS systems

TransformersOperating low-voltage tung-sten halogen lamps requirestransformers with an outputvoltage of 6 V, 12 V or 24 V.

A distinction is made betweenconventional and annular coretransformers; the difference isless a matter of power dissi-pation than of size.

Additional features providedby electronic transformersinclude automatic shutdownin open circuit, ability towithstand short circuits, andgentle starting for longerlamp life.

Transformers for low-volt-age lamps turn the 230 Vsupply voltage into a lamp-operating voltage of 6, 12 or24 V. On the secondary sideare correspondingly high cur-rents requiring a significantincrease in the cross-sectionof the transformer windingand of the lamp connectioncable.

Advantages of electronictransformers

compact size

low weight

low power dissipation

low internal resistance

no noise generation

high efficiency

overload and overheating

prevented by power control

without lamp deactivation

non-encapsulated, therefore

repairable if defective

soft starting - no current

peaks on activation

electronic protection against

short-circuiting

To compensate the induc-tive reactive power of con-ventional (CB) and low-lossballasts (LLB), luminaires withfluorescent lamps are fittedwith a capacitor parallel to theline connection (230 V).

P.f. correction capacitorsP f. correction capacitorsserve to improve the powerfactor. They reduce theinductive reactive power ofthe ballasts (chokes) thatcontributes to the load onthe electrical equipment, e.g.leads, cables, transformersand switches. Power utilitiesstipulate that p.f. correctioncapacitors need to be usedin luminaires with dischargelamps.

P.f. correction capacitorsmust bear the symbol F(flameproof) or FP (flame-and explosion-proof), display

a test symbol from a recog-nised testing agency and beequipped with a dischargeresistor.

P.f. correction capacitors arenot required where EBs areused.

Starters and ignitersStarters for fluorescent lampscomplete or open the preheat-ing current circuit of a fluores-cent lamp and thereby initiatethe ignition process. A distinc-tion is made between univer-sal and fused rapid starters.Starters are not requiredwhere EBs are used.

Metal halide lamps and high-pressure sodium vapourlamps need a starting volt-age pulse of the order of1 to 5 kV. Igniters with specialelectronic switches are thusused to ignite high-pressuredischarge lamps.

For the immediate hot re-igni-tion of extinguished metalhalide or high-pressuresodium vapour lamps, ignit-ers with voltages consider-ably higher than 5 kV arerequired.


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Low-voltage installationBecause of their low operatingvoltages, low-voltage installa-tions constitute no immediatehazard to human beings. Itneeds to be borne in mind,however, that the stepped-down voltage gives rise tovery high currents.(Example: lamp 230 V, 100W: current I = 0.43 A; lamp 12V, 100 W: current I = 8.33 A).

If cables, contacts, terminalsor switches are not ade-quately dimensioned, thesehigh currents can cause over-load. To avoid fire hazards insuch cases, special installa-tion requirements need to beobserved.

Low-voltage plug-in systems,with plugs, couplings andcables, have a proven trackrecord here.

Regulation and controlLighting regulation and controlplay a central role in modernbuilding service management.As well as the energy savingsthey permit, they are increas-ingly appreciated for the con-venience they provide and themotivational boost deliveredby dynamic lighting.Lighting can be adjustedaccording to the amount ofnatural light available or theposition of the sun (daylightcontrol or regulation), accord-ing to whether the room isin use (presence detection)or according to the lightingatmosphere required (e.g.RGB control).Dimmer control of GLS or230 V tungsten halogenlamps presents no problemswith leading phase-anglecontrol dimmers.

Low-voltage tungsten halo-gen lamps operated on aconventional or annular-coretransformer need a specialdimmer geared to the behav-iour of the transformer in dim-ming operations.Lamps used in combinationwith electronic transformerscan only be regulated by spe-cial leading or lagging phase-angle control dimmers, andattention should be paid to themanufacturers information.Controllable EBs permit infi-

nite flicker-free adjustment offluorescent lamps down to 1%luminous flux.

Central management ofbuilding installations- Bus systemsThe increasing complexityof building technology andthe control and monitoringof all building installationand service systems, e.g.heating, air-conditioning,alarm and security systems,lighting, window blind controletc., require a new approachto building management thatincorporates all the individualsystems including lighting in an intelligent controlsystem.

Microelectronics and datatransmission techniques makeit possible for all the neces-sary system groups to com-municate with each other viaa shared bus network.

Information from sensors (e.g.photoelectric barriers, infra-red receivers, wind gauges,brightness sensors) is con-veyed by the bus network.The appropriate assignmentof sensors (receivers) andactuators (switches) permitsa wide variety of functionsto be programmed for controland regulation.

DALI digital lightingmanagementDALI (Digital AddressableLighting Interface) is an intel-ligent lighting managementsystem specifically developedto meet the requirements ofmodern lighting technology.Easy to use, cost-efficientand designed for use withinterface modules permittingintegration in building man-agement systems with EIB(European Installation Bus)or LON (Local Operating Net-work) circuitry.

DALI controls lighting throughall DALI components and canaddress each appliance indi-vidually. It can assign eachEB (= luminaire) equally, forexample, to as many as 16groups, define 16 lightingproduction attributes for each

individual fitting or dim all EBstogether in one synchronizedoperation.

The members of AG-DALI,the DALI working group inthe German electrical andelectronic manufacturersassociation ZVEI, includeleading European and USmanufacturers of electronicballasts and lighting controland regulation systems.

Dimming thermal radiators:correlation of wattage andluminous flux.


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Luminaires

Recessed louver luminaires

Surface-mounted louver luminaires Direct/indirect pendant luminairewith optical control panels

Recessed wallwashers

with asymmetrical beam

Medical supply unit, horizontalwith direct/indirect beam

Floodlightswith asymmetrical beam

Awide variety of luminaires are available to cater to thediverse technical and design requirements of the broadrange of lighting applications.

The examples shown on these two pages are only a smallselection. In particular, they do not include luminaires designedfor special applications, such as tunnel luminaires, buildingsecurity luminaires, luminaires for explosive atmospheres, air-conditioning luminaires and clean room luminaires.

More information about luminaire systems and manufacturersis available on the internet at www.licht.de.

Spots on power track

and swivellable recessed downlights


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Direct/indirect recessed luminaires Downlightswith symmetrical beam (left)and asymmetrical beam (right)

Direct/indirect standard office luminairewith desktop luminaire

Escape sign luminaire

for identifying escape route

Post-top luminaire (left)Light stela (right)

Wall luminaires

as surface-mounted luminaire (left)and as recessed luminaire (right)

Bollard luminaireRecessed ground luminaire

Direct/indirect standard domestic luminairewith tabletop luminaire


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Lighting planning

Interior lightingInterior lighting systems needto conform to the relevantstandards.

For planning a lightingsystem, the following areneeded: groundplan and sectionalviews of the rooms, withroom dimensions

details of ceiling construction, colours and reflectance ofceilings, walls, floors andfurnishings

purpose of the room, pro-posed visual tasks

location of work zones arrangement of furnitureand/or machines

operating conditions, e.g.temperature, humidity, expo-sure to dust

Appropriate light sources and

luminaires should be selectedon the basis of these data.After the number of lampshas been calculated for theilluminance required, thenumber and arrangementof luminaires can be deter-mined. Lighting, mountingand maintenance factors, andarchitectural considerationsall play an important role inthe planning process.

The architects preferencesfor certain types of luminaire

and luminaire arrangementsneed to be balanced againstan appreciation of lightingtechnology and ergonomics.

As well as the technicalaspects of lighting, the econ-omy of a system must also betaken into account.

Lighting planning by thelumen methodThis method is described inProjektierung von Beleuch-tungsanlagen nach demWirkungsgradverfahren(Planning lighting systemsby the lumen method), whichis published by the DeutscheLichttechnische GesellschafteV (LiTG) and also includesutilance tables for a numberof standard luminaires.

The number of luminairesrequired for any desired illumi-nance can be calculated usingthe following formula:

Key

n number of luminairesE illuminance requiredA area or partial area of

roomz number of lamps per

luminaire luminous flux of a lampLB light output ratio

R

utilanceB LB R coefficient of

utilizationWF maintenance factor

n = E Az B WF

Illuminance levels on work-ing plane, floor, ceiling andwalls can be computed anddisplayed as isolux curves bylighting planning software.

The computer simulationof the illuminated squareand adjacent street at nightprovides a realistic view ofthe installation in operation enabling the lighting desig-ner to check his or her work.

Planning software compu-tes the illuminance at a largenumber of points in the roomand produces a graphic dis-play of the results.

Utilance is a function of theluminous flux distributed bythe luminaire, the geometryof the room and the reflect-ance of room surfaces.

The coefficient of utilizationB includes the light outputratio LB and the utilance R.Extensive tables of coeffi-cients of utilization B aresupplied by luminaire manu-facturers.


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Planning lighting with com-puter softwareThe lumen method is usedto calculate the number ofluminaires required for agiven mean illuminance. Theilluminance calculations atdifferent points in the roomare performed by computer.Special software is availablefor this purpose.

Using menu-driven inputs,lighting planning softwareprovides a complete set oflighting calculations - frominitial rough outline to fullydocumented, comprehensiveproposal.

Numerous help functions areavailable at the touch of akey; graphic displays facilitate

input and the interpretation ofresults. Computer graphicsprovide a realistic image ofthe lighting system.In addition to furnishing thetechnical documentation for alighting project, programs canalso draw up a list of materialstogether with a breakdown ofthe luminaires of each typerequired in the room, includ-ing a descriptive text.

Planning software enablescomputed results, such asthe illuminance values on theevaluation plane, to be viewedin the form of a grey-tonediagram.

Street lightingThe purpose of street light-ing is to improve road safetyduring darkness. It can onlydo so, however, if it meetskey lighting criteria.

This entails satisfying theminimum requirementsneeded to enable drivers tomake out shapes and move-ments at a safe distance andthus respond appropriately tothe presence of people andobjects in the traffic area.

The challenge for the lightingplanner is to meet the require-ments laid down in road safetystandards and regulations forluminance, longitudinal andoverall uniformity and glarelimitation. The result should

be a clear image of the roadahead.

Capital expenditure, operatingand maintenance costs needto be low to ensure an eco-nomical lighting system. Andthe luminaire arrangement,the types of luminaires andthe lamps used in them needto be selected to produce anoptimal solution for the geome-try of the road.

As for the choice of appro-priate luminaires, the mosteconomical options are lumi-naires with specular opticalsystems for high-pressuredischarge lamps.

To calculate the averageroadway luminance and uni-formity of luminance, it is nec-essary to know the luminousintensity distribution of theluminaires, the luminous fluxof the lamps, the geometry ofthe installation and the reflec-tive properties of the road sur-faces. The figures for the lastparameter can be taken fromstandard road surface tablesor obtained by measurement

using a road reflectometer.

This printout shows theluminaires and the impact ofthe lighting on the furnishedroom.

Another photorealisticcomputer image: here, theimpact of lighting on a car parkat night.


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K = n1

[k1

K1 + k2

K2100 100 Capital costsn2

[+ n1[ tB a P]

+ n1[tB (K3+ K4) +R]n2tL

Energy costs

Lamp replacementSystem maintenance

Lighting costs

Whether new systemsare being installedor old systems refur-

bished, energy consumptionand cost are important criteriafor lighting system planning.Project planning thus needsto include an energy-balancecalculation and an economicfeasibility study.

Cost comparisons only makesense where the quality, ser-vice life, serviceability andmaintenance requirementsof luminaires as well as theavailability of spare parts andcompliance with lighting qual-ity features are comparableand guaranteed.

Appropriate, precise plan-

ning, competent selection oflamps, operating devices andluminaires, and an optimalluminaire arrangement

lighting with artificial light

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