Good Lighting for Museums Galleries and Exhibitions

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    Frdergemeinschaft Gutes Licht

    Good Lighting for Museums,Galleries and Exhibitions 18

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    FREE-STANDING EXHIBITS

    REVOLVING EXHIBITION

    ENTRANCE AREA

    EXHIBITS ON WALLS

    EXHIBITS IN SHOWCASES

    Contents

    Cover photograph: Lighting creates visual

    experiences in any exhibition. Modulatingand accentuating the visual landscape, it

    enhances the impact of a presentation.

    Lighting is vital for spatial impression and

    enjoyment of art.

    Visual experiences 1

    The action of light 2

    Exhibits in the limelight 6

    Showcase lighting 8

    Revolving exhibitions 10

    Foyers, corridors, staircases 12

    Audiovisual media 14

    Lecture room 15

    Library 16

    Study room 17

    Cafeteria, museum shop 18

    Workplace lighting:office, workshop, storagefacilities 19

    Outdoor exhibits 20

    Night scenes 21

    Daylight 22

    Lighting management 24

    Vision, recognition, perception 26

    Light protection 30

    Maintenance 33

    Lamps 34

    Luminaires 38

    Standards and literature 42

    Acknowledgements 43

    Imprint 44

    Information fromFrdergemeinschaftGutes Licht 45

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    OUTDOOR EXHIBITS

    MUSEUM SHOP

    CAFETERIA

    OFFICE

    WORKSHOP

    STORAGE ROOMS

    ART

    SCIENCE

    TECHNOLOGY

    HISTORY

    CULTURAL HISTORY

    HISTORICAL

    FIGURES

    LECTURE ROOM

    STUDY ROOM

    LIBRARY

    Around 100 million people ayear visit Germanys museumsto view, experience, admireand enjoy their exhibits. There

    are more than 6,000 such in-stitutions in total, with a widevariety of collections, a broadspectrum of specialisationsand presentation concepts thatrange from hands-on displaysfor an interactive experience toquiet retreats for silent contem-plation. What they all have incommon, however, is that theyseek to inspire the visitor.

    Whether the focus is art or sci-ence, technology or history, thepresentation needs to be ap-pealing, interesting and varied.And that is where lightingplays an important role: it cre-ates visual experiences in anyexhibition, it helps modulateand accentuate the visuallandscape, it enhances the im-pact of the items on display.The visual ambience must notcause fatigue. On the contrary,it should stimulate but notconfuse. In large buildings, dif-ferentiated room design is alsoa requirement.

    Light spacesLighting is vital for spatial im-pression and enjoyment of art.Different light colours andbeam spreads, different de-signs and arrangements ofluminaires and lamps createdifferent lighting situations light spaces designed tomeet the relevant needs of theexhibition.

    Special attention needs to be

    paid to conservation require-ments. Light protection playsan important role in any exhi-bition room.

    There is more to a museumthan just what it displays; it isalso a place of research,where collections are stored,preserved and managed. Onlyin the right lighting can muse-um staff work effectively. Light-ing also draws attention to trip-ping hazards and reduces the

    risk of accidents. So althoughthe lighting designer has agreat deal of freedom in exhi-bition rooms, functional lightingmust always be provided.

    Visual experiences

    1

    Fig. 1: The graphic above shows

    a virtual museum: most of the

    space is occupied by the exhibi-

    tion area (blue), followed by the

    general public areas (red) andthe rooms which serve as work

    premises (orange). The outdoor

    area (green) is surrounded by

    the building.

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    The design and configura-tion of exhibition roomlighting depends on manyplanning parameters. Fore-most among these is thearchitecture of the buildingwith which the lighting isrequired to harmonise. Oth-er factors are room propor-tions, interior design, colourscheme, available daylightand, last but not least, thenature of the exhibition. Theway the ambience is

    shaped by light and shad-ow is a matter of funda-mental importance.

    Room lightingLighting for exhibitionrooms in museums ismade up of diffuse and di-rectional light. The relativeamounts and resulting mixof the two types of light de-termines the harshness ofthe shadows cast by pic-ture frames and the three-dimensional impact ofsculptures and spatial ob-jects. The diffuse and di-rectional light mix also de-

    fines the overall impressionmade by the room.

    A closely related matterhere is the distinction be-tween room and exhibitlighting. The diffuse lightingis almost all generated bythe room lighting, whichdetermines the distributionof brightness and sets light-ing accents in the horizon-tal plane.

    Room lighting alone israrely enough to meet allan exhibitions needs.Conversely, the directionallighting used to illuminate

    exhibits does not providebright enough roomlighting except in a few mostly small and bright interiors.

    Exhibit lightingExhibit lighting uses hard-edged directional light toaccentuate individual itemson display. As a generalrule, it needs to be supple-mented by softer roomlighting. Exhibit lighting

    based on spots alone isadvisable only where a par-ticularly dramatic effect isrequired.

    Otherwise, a stimulatingspatial experience is ob-tained with a mix of diffuse(room) and directional (ex-hibit) lighting.

    Diffuse lightingDiffuse lighting illuminatesroom zones or objects

    from a surface that radiateslight in all directions. At thesite of illumination, i.e. inthe room zone or at theobject illuminated, the di-

    rection from which the lightcomes cannot be clearlydetermined: the light flow-ing into the room and overthe objects is not direction-al. Where it comes fromvery many directions, i.e.where the radiant surfaceis large, the lighting pro-duces little or no shadow-ing.

    Directional lightingDirectional lighting is gen-

    erated mostly by punctuallight sources i.e. lampsthat are small in relation tothe lighting distance orspots of similar design. Thelight falls directly onto theobject illuminated, strikingit, or parts of it, at an angledefined by the geometry ofthe lighting arrangement.Where the surface of theobject is uneven, clearlydefined shadows occur.These enhance the visual

    impact of three-dimension-al surfaces but can also bea source of visual interfer-ence if they are too domi-nant or too large.

    The action of light

    2

    Light protectionDaylight and artificiallight contain rays whichmay fade, dry out,discolour or deformexhibits. Conservationmeasures can protectagainst this but only ifthey are properly applied

    and observed. For moreabout light protection,see page 30.

    Route lightingIn some exhibition rooms,

    visitors are free to move

    around in any direction. Inmany others, however, be-

    cause of the nature of the ex-

    hibition or for organisational

    reasons, they need to be di-

    rected. Luminaires which

    highlight routes without inter-

    fering with the display areas

    on either side are a practical

    solution for this task. Also

    practical and stylish as well

    is (additional) floor-level

    orientation lighting, e.g. with

    LED lighting strip.

    Photo 1: Ambience and the way

    we experience a room are

    shaped by light and shadows

    and the way they are mixed.

    Photo 2: Diffuse lighting is

    predominantly used for general

    room lighting.

    Photo 3: Illuminating objects

    exhibits are set off to dramatic

    effect by directional lighting1

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    Diffuse/directionallightingIn many applications, light

    cannot be clearly definedas wholly diffuse or whollydirectional. This is the casewhere the surface radiatingthe light is neither large norpunctual e.g. a spot witha diffuser disc. Dependingon the diameter of the discand on the lighting dis-tance, shadows are nar-rower or wider, harsher orsofter.

    Diffuse/directional lighting

    also occurs where a sur-face is illuminated or back-lit to produce diffuse light-ing and part of the light ismade to radiate in a partic-

    ular direction and is thuspartially directional. The di-rection from which the light

    comes can be seen on theobjects illuminated. Howev-er, the shadowing that oc-curs on exhibits is lessclearly defined than if thelight were entirely direction-al. The modelling is ren-dered more subtle by thebrightening effect of the dif-fuse lighting component.

    Diffuse/directional lightingcan also be produced, forexample, by linear lamps in

    appropriately designed lu-minaires. Here, shadowingdepends on the position ofthe luminaire in relation tothe picture: wallwashers

    3

    Fig. 2: Directional lighting for the

    wall, diffuse lighting for the room

    Fig. 3: Supplementary directional

    lighting for objects in the room

    Fig. 4: Indirect and direct

    components produce diffuse and

    directional lighting respectively

    Fig. 5: Solely directional light

    with tubular fluorescentlamps mounted horizontallyor parallel to the upper

    edge of the wall producehard-edged shadows be-neath horizontal pictureframes, whereas the shad-ows cast by the vertical partof the frame are barely dis-cernible.

    Avoiding cast shadowsDirectional light producesform shadows. Where italso results in cast shad-ows on neighbouring ob-jects, the hard contours and

    obscure origin of suchshadows are disturbing.Cast shadows are avoidedby ensuring an appropriatemix of diffuse and direction-

    al light, correct positioningof the light source produc-ing the directional light or

    appropriate positioning ofthe illuminated objects inrelation to one another.

    2

    3

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    The most important lightingsystems used in exhibitionrooms are:

    luminous ceilings withopal glass enclosure (dif-fuse light) or satinised andtextured glass (diffuse/directional), indirect luminaires (dif-fuse), cove luminaires (diffuse), wallwashers (directionalor diffuse/directional), spot lamps.

    Luminous ceilingsThe idea of luminous ceil-ings stems from a desire toimitate daylight. Luminousceilings deliver light which isparticularly suitable forpainting galleries predom-inantly diffuse with an opalenclosure, partly directionalwith enclosures of sa-tinised/textured glass. Theheat that is generated in anyluminous ceiling needs tobe dissipated or extracted.

    The light sources of choiceare tubular fluorescent

    lamps arranged accordingto the structural grid of theluminous ceiling. For gooduniformity, they should bespaced no further apartthan the distance to theceiling enclosure. The sizeof the luminous ceiling,its subdivision and the tran-sitions between ceiling andwalls need to suit the pro-portions of the room andthe nature of the objectsdisplayed.

    Luminous ceilings imitatingnatural daylight need todeliver a high level of lumi-nance: 500 to 1,000 cd/m2,ranging up to 2,000 cd/m2

    for very high-ceilingedrooms. Luminous ceilingsare especially suitable forinteriors with 6 metre ceil-ings or higher. Where roomheights are lower, their lightcan dazzle because theyoccupy a large part of the

    field of vision. Where thelighting is dimmed for con-servation reasons or to re-duce glare, the luminousceiling loses its daylight

    The action of light

    4

    Photo 5: Indirect lighting has

    an impact similar to that of a

    luminous ceiling.

    Photo 4: Luminous ceilings are

    particularly suitable for painting

    galleries. The cove lighting

    provides additional brightness.

    4

    5

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    quality and looks grey andoppressive. All luminousceilings including day-lighting installations need

    to be designed by a spe-cialist.

    Indirect luminairesAn impact similar to that ofa luminous ceiling isachieved with indirect lightbounced off the ceiling andupper wall surfaces into theroom. This diffuse, uniformlight is predominantly usedin rooms where no daylightenters. It is produced bysuspended luminaires radi-ating light upwards.

    In exhibition rooms, for ex-ample, luminaires for sus-pended power track sys-tems are an option: theyare inserted in the trackfrom above while spots fordirectional lighting are ac-commodated in the lowerchannel.

    Cove luminairesThe diffuse light of lumi-naires installed in the curv-

    ing transition between walland ceiling the cove orcoving is another indirectlighting solution. The coveluminaires most frequentlyused in modern museum

    buildings are models withhousings which themselvesform the coving.

    The main direction of lightwith cove lighting is closerto the horizontal than with aluminous ceiling and corre-sponds roughly to that ofperimeter luminairesmounted in continuousrows. The light is largelyshadow-free. Linear lamps generally tubular fluores-cent lamps are the mostwidely used light source.

    Excessive luminance at theceiling and on the upperpart of walls causes glareand interferes with spatialexperience. This can occurin coves where no stepsare taken to provide opticalcontrol for example be-cause the existing cove of-fers no space for prisms orreflectors. Where simplenon-overlapping battensare installed, disturbinglight-dark transitions arealso visible around the lam-pholders.

    WallwashersWallwashers are used as in-dividual luminaires or incontinuous rows. Installedflush with the ceiling (or with

    kick reflector protrudingfrom the ceiling) or mount-ed close to the ceiling, theyshould illuminate the walls

    as uniformly as possible.This task is performed byreflectors with asymmetricaloptics. It is important to en-sure good shielding in thedirection of the observer. El-ements on the luminaire formounting accessories such as filters or anti-glareflaps are useful.

    Favoured light sources forwallwashers include linearlamps: fluorescent lamps,compact fluorescent lampsin elongated designs, linearhigh-voltage halogenlamps. The diffuse/direc-tional lighting delivered bythe continuous rowarrangements that are pos-sible with these lightsources produces relativelydeep shadows, especiallyalong the horizontal edgesof picture frames.

    The directional light deliv-ered by individual lumi-

    naires with non-linearlamps, on the other hand,gives rise to additionalshadows along the horizon-tal edges of a pictureframe.

    Spot lampsReflectors in reflector lamps(used in luminaires with noreflector) or spots direct

    most of the light emitted bypunctual light sources in adefined beam direction.Spots and downlights withspot characteristics can befully or partially integratedinto a ceiling (or wall) asrecessed ceiling spots. Sur-face-mounted ceiling spotsand downlights as well asspots for power track havevisible housings. Elementson the luminaire for mount-ing accessories such asfilters or anti-glare flaps are useful.

    Punctual light sources in-clude high-voltage halogenlamps and low-voltagehalogen lamps with andwithout reflector, incandes-cent lamps with or withoutchrome cap as well as met-al halide lamps.

    5

    Photo 6: Wallwashers distribute

    their light asymmetrically.

    Photo 7: The directional light of

    spot lamps raises the

    brightness for exhibits here

    with an appropriate beam angle

    for paintings.

    6 7

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    Exhibits in the limelight

    6

    Medium-scale, large andvery large exhibits and thelight that falls on them areseen to full effect only from

    a distance. This must beborne in mind when the ex-hibits are positioned.

    Viewing withoutinterferenceTo ensure that all exhibits areshown to their best advan-tage, neither the room northe exhibit lighting should in-terfere with the visual task:

    There should be noevocative shadows or pat-terns of light on walls or ceil-ing. Such visual interferencedefinitely needs to be ruledout for exhibition walls. Reflections and undesir-able shadows on picturesand objects should beavoided. With direct lighting,the way to guard againstthis is to position luminairesso that the distance fromthe exhibit is around a thirdof the height of the wall. No cast shadows shouldfall on neighbouring ex-

    hibits. A greater distance be-tween wallwashers and wallmakes for better uniformitybut presents a risk of directglare. The compromise be-tween uniform illuminationand visual comfort: the an-gle between luminaire andwall down to the lower limitof the presentation areashould be between 25 and30 degrees (see Fig. 6 + 7)

    Reflectance in the roomThe colour, pattern and re-flectance of ceiling, wallsand floor affect the visualimpact of the exhibits andthe atmosphere of the room.How bright or dark wallsand ceiling can be kept i.e. how high their re-flectance should be de-pends crucially on the de-sign intention. It is not pos-sible to make a general rec-ommendation.

    What kind of light haswhat impact?An exhibit in the limelightis (almost) always an exhibit

    in directional light. Whathappens when changes aremade in direction of lightand beam angle? What doobjects look like with andwithout bright surroundings?What difference can lumi-naire accessories make?Answers are found in thephotographs on page 7,where a portrait and a non-figurative painting are pre-

    sented as examples of two-dimensional pictures and afragment of an ancientsculpture and a red vase forthree-dimensional objects.

    Basically speaking, the im-pact of any change onthese relatively small ex-hibits is the same for large-scale pictures and objects.The only difference is thatthey need more light: high-er power lamps or greaternumbers of spots need tobe used for illuminatinglarge objects. A very largeobject, such as a car or a

    plane, can also be illumi-nated from several points.This makes for striking vi-sual impact from variousviewing angles.

    Text panelsPrinted information aboutan exhibit is useful only if itis legible which is alwaysthe case with adequatelylarge black type on a whitebackground. Where differ-

    ent lettering is required, itshould be tested for legibili-ty in advance. And alwaysremember: legibility is im-paired by reflections.

    C

    B

    A

    1 m

    1.6 m

    Smallest

    observation

    distance

    Greatest

    observation

    distance

    60 floodlight angle

    30 optical axis

    30 spotlight opening angle

    x

    70

    30

    100 critical obser-

    vationz

    one forvertical illumi-

    nation

    Line ofview-

    ing

    Edges o f picture

    Visitor area

    1.

    65m

    y

    y

    30

    4.00

    (y = 2.35)

    x

    1.

    65

    m

    3,30

    (y = 1.65)

    2,70

    (y = 1.05)

    x = y tan 30

    Roomheight

    x =Distancespot/wall

    2.7 m 0.60 m3.3 m 0.95 m4.0 m 1.35 m

    Line of v iewing

    Fig. 6 + 7: Calculation of the optimal positioning of a luminaire for pictures on a wall room height,

    observation zone, size of picture and optimal viewing angle (fig. on left) are the parameters defining

    the optimal position of a wall-lighting luminaire. The upper edge of the picture determines the spotlightopening angle (B: 30, C: 60) with a constant angle of inclination of 30. Angles less than 30 can

    result in reflections at the upper edge of the picture (critical observation zone). The mathematical

    formula for calculating the distance x between spotlight and wall for illuminating a picture with the

    height y is: x = y tan 30 (fig. on right).

    Photo 8: Higher power lamps or

    multiple spots are used for illu-

    minating large-scale objects.

    8

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    7

    Spot with 15 beam angle and

    ambient luminescence

    Spot with 15 beam angle and

    diffuse ambient luminescence

    Contour spot with no ambient

    luminescence

    Diffuse ambient luminescence

    Spot with 15 beam angle and

    soft focus lens

    Spot with 45 beam angle and

    oval lens

    Wallwasher with asymmetrical

    light distribution fitted with R7s

    halogen lamps (230 V)

    Spot with 15 beam angle,

    lighting from front, top, middle

    Spot with 15 beam angle, light-

    ing from front, top, left

    Spot with 15 beam angle, light-

    ing from front, bottom, left

    Side lighting from right

    Lighting from front Lighting from back Lighting from right Lighting from above

    9 10 11 12

    13 14 15 16

    20191817

    21 22 23 24

    Wallwasher with symmetrical

    light distribution fitted with R7s

    halogen lamps (230 V)

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    Showcases are miniatureexhibition rooms and theexhibits they contain needto be illuminated accord-ingly with diffuse or direc-tional light. In some cases,illuminating and accentuat-

    ing light may also be mixedin glass display cabinets.

    The right light for the taskThe type of lighting re-quired depends essentiallyon the characteristics of theexhibits on three-dimen-sional form, structure, sur-face gloss and transparen-cy or colour.

    Most metal objects goldor silver receptacles, for

    example acquire a fasci-nating beauty when theygleam. And that gleam

    occurs when they are illu-minated by punctual lightsources. Under diffuselighting, the receptaclesappear matt and lifeless.

    For transparent or translu-

    cent objects such as glassexhibits, the key to height-ening visual impact liesmore in modelling than ingleam. The structure ofsurfaces cut, etched orpainted also plays an im-portant role here. Depend-ing on the exhibit, thecorrect solution may be dif-fuse or directional lighting(through-lighting) or acombination of the two.With directional lighting,

    visual impact is determinedby the angle of light inci-dence. Diffuse lighting is

    appropriate for coloured ortransparent materials suchas glass windows.

    Integrated lightingSmall, shallow display cabi-nets (glass-topped desks)

    and high or box-shapedshowcases mostly have anintegrated lighting system.This has advantages: Fewer or no reflectionsoccur on the cabinet glass. It is easier to avoid directglare for the observer dueto bright unshielded lightsources. It is easier to engineerspecial lighting effects for adramatic presentation.

    In small display cabinets,exhibits are normally illumi-nated from the side. In highshowcases, lighting fromthe cabinet roof is an op-tion. Alternatively, objectscan be bathed in light frombelow from the base of thecabinet.

    In addition to the lightingintegrated in the showcase,separate ambient lighting isgenerally essential. De-

    pending on the atmosphererequired and the illumi-nance permitted for conser-vation, the room lightingshould be just below the

    level of the showcase light-ing or even lower. Orienta-tion lighting which reliesentirely on stray light fromshowcases and not on adedicated orientation light-ing system should not betoo low.

    Light protection

    Light protection (see page30) is also an importantconsideration for showcaselighting not least becauselamps in showcases areoften closer to exhibits thanin exhibition rooms. It mustalso be borne in mind thatthe enclosed space of ashowcase has its ownmicroclimate.

    For the lighting, there arealternatives to the lamps

    used in the past: LEDs, forexample, which deliver abeam that contains no IV orIR radiation, and fibre-opticlighting systems, which

    Showcase lighting

    8

    Photo 25: Under the top-down

    showcase lighting, the suits of

    armour gleam in fascinating

    detail

    Photo 26: LEDs for light protec-

    tion luminous diodes emit

    neither ultraviolet light nor heat.

    25 26

    Fig. 8 + 9

    Directional

    lighting (left)

    accentuates

    exhibits,

    planar lighting

    (right) makes

    for uniform

    illumination.

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    have a very low UV/IRcontent. Incidentally, be-cause of their size, both ofthese solutions are alsosuitable for illuminating verysmall display cabinets.

    For fluorescent lamps,compact fluorescent lampsand high-voltage and low-voltage halogen lamps, thesame safeguards are re-quired in showcases as inlarge exhibition rooms.

    External lightingRoom and object lightingoutside showcases is gen-erally provided by ceilinglights. This type of lightingis particularly suitable for

    all-glass cabinets andshallow glass-topped deskshowcases for viewing fromabove. Daylight and object-oriented room lightinggenerally need to be sup-plemented by accentuatingexhibit lighting. Whereluminaires are arranged tosuit showcases, there islittle risk of reflected glare.

    Limiting reflectionsLimiting reflected glare is

    an important considerationwhatever kind of lighting isinstalled for showcaseswith horizontal and verticalglass surfaces. Effective

    bright internal lighting thuspresent a lower risk.

    Reflections can also becaused by windows(daylight). Appropriatepositioning of showcases

    or daylight screening e.g. with vertical blinds prevents this kind of re-flected glare.

    9

    protection against reflectedglare is provided by non-reflecting glass.

    Reflections on horizontalglass surfaces occur lessfrequently if the glass is tilt-

    ed towards the observer.How visible they are de-pends on the degree ofcontrast with the surround-ings, i.e. the darkness ofthe showcase. Light-coloured showcases with

    Photo 27: The manuscripts in

    the showcase walls are

    uniformly illuminated from top

    to bottom.

    Photo 28: Reflection-free

    external lighting illuminates and

    highlights the books in the

    cabinets.

    Photo 29: Where luminaires

    are arranged to suit showcases,

    ceiling lighting is largely

    reflection-free.

    27 28

    29

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    Exhibits which are not onpermanent display or whichgo on tour are presented inrooms for revolving exhibi-

    tions. Each new show is anadded attraction and drawsnew visitors to see the per-manent exhibition.

    To cater for a regularchange-over of exhibits,lighting systems need to beadaptable. So very flexiblelighting is required. Itshould be noted, however,that absolute flexibility enabling the lighting to beas finely tuned for everytemporary presentation asfor a permanent exhibition is an unattainable goal.

    Flexible lightingThe general diffuse lighting takes little accountof the positioning of ex-hibits. The flexibility of thesystem depends on thedirectional lighting. Particu-larly suitable solutions hereare furnished by powertrack systems, in which

    swivellable, rotatable spotscan be snap-mounted atany point. Part of the powertrack installed should be

    mounted along the walls topermit gallery-style walllighting. In the rest of theroom, rectangular or squarearrangements of powertrack make for greater flexi-bility than an arrangementin just one direction.

    An alternative to powertrack are stationary gimbal-mounted spots. These canalso be set at any angleand servomotors can beused for re-angling andfocusing. Gimbal spotlightsare not quite as flexible asspots on power track butthey permit a ceiling thatmakes a much moretranquil design statementthan one with power track.

    Realigning luminairesThe luminaires of a flexiblelighting system need to berealigned for each newrevolving exhibition if

    necessary by experimentingand repositioning exhibits.This invariable calls for theuse of ladders and steps.

    For inaccessible locations,remote control spots arethe right answer.

    Taking account ofdaylightWhere revolving exhibitionsare staged in daylit rooms,daylight incidence and theposition of showcases inrelation to windows (seepage 9) must also be takeninto account. To maximizethe scope for catering toexhibition requirements, itis best to ensure that daylitrooms can be fully dark-ened. More informationabout daylight is found onpages 22/23. Facilities fordarkening rooms can alsobe useful for light protec-tion; for information aboutthe light protection require-ments of exhibits whichnaturally also need to bemet in revolving exhibitions see pages 3033.

    Mobile spotsWhere mobile partitions areused for presentations,mobile spots fastened to

    the partitions by clamps orscrew mountings are analternative to spotlights onpower track. So that powercables to spots do notpresent a tripping hazard,rooms for revolving exhibi-tions should be providedwith power points in thefloor.

    Revolving exhibitions

    10

    Photo 30: The light of the

    gimbal-mounted spots is focus-

    able.

    30

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    11

    Photo 31: Power track is

    integrated in the ceiling grid

    construction to accommodate

    the spotlights for the exhibit

    lighting.

    Photo 34: The spotlights need

    to be repositioned for every

    new revolving exhibition.

    Photo 32: Power track integrated

    in the ceiling makes it possible

    for spots to be positioned in

    flexible arrangements.

    Photo 33: High illuminance

    where required each

    luminaire features four gimbal-

    mounted spots.

    31

    32

    33 34

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    12

    The entrance area is thecalling card of the estab-lishment. It shapes visitorsfirst impressions, its design

    can overcome fear ofcrossing the threshold. Aharmonious lighting atmos-phere sets the scene for afriendly reception. Foyersalso serve a functional pur-pose: they lead into the in-terior of the building.

    Harmonious lightingTo meet these require-ments, the lighting needsto incorporate a mixture of

    direct and indirect light delivered by a combinationof lighting systems de-signed to cater for everylighting task: the uniformgeneral lighting providessecurity and facilitates ori-entation, accentuating light

    on ceiling and walls makesthe visual impact lesssevere. Direct or direct/in-direct luminaires with

    efficient fluorescent orcompact fluorescent lampsare the most widely usedlight sources for the gener-al lighting; wall luminairesfor indirect lighting formpart of the accent lighting.

    In the entrance zone, peo-ple step out of bright day-light into a darker buildingor out of night-time dark-ness into a brightly lit interi-or. To enable their eyes toadjust to the change inbrightness level, adaptationzones are recommended.During the day, the immedi-ate entrance area needs tobe particularly brightly lit;at night, the illuminanceinside the building shoulddecrease towards the exit.

    The calling card role of afoyer makes it an interest-ing place for special archi-tectural features featureswhich lighting and lighting

    characteristics shouldunderline. For high ceilings,for example, high-intensityspots with high-pressuredischarge lamps are re-commended. As pendantluminaires with direct/indi-rect light distribution, theyemphasize the height ofthe room. Moulded plasterceilings, columns orgalleries can be very effec-tively stressed by accentu-ating light.

    Guiding lightCorridors, staircases andlifts connect the entrancearea with the deeperrecesses of the building.If they are significantlydarker than the foyer, theycan be off-putting. To avoidthis tunnel effect, the illumi-nance realised should

    either be the same or re-duced very gradually instages. DIN EN 12464-1stipulates a minimum of

    100 lux illuminance forcirculating areas such ascorridors.

    A route guidance systemprovides an effective addi-tional orientation aid forvisitors. To ensure reliableguidance, it should includebright information panels orback-lit signs with a clearmessage.

    Safe lightThe risk of tripping onsteps and stairs is reducedby good lighting. The illu-minance should be at least150 lux (DIN EN 12464-1).As it is generally moredangerous to fall downstairs than to trip on theway up, it is particularlyimportant that the lightingshould ensure that treadsare clearly discernible fromabove. In addition, lightfalling from the upper land-ing makes for short soft-

    edged shadows. Thetreads can thus be clearlydistinguished; each one isreadily identifiable.

    Floor-level orientationlighting provides addedsecurity. Wall lights at theside of the stairs castingdirect light onto treads area solution here. LED tech-nology offers a new alter-native, e.g. with luminousdiodes set into risers. LEDs

    are also used for illuminat-ing banisters.

    Foyers, corridors, staircases

    Photo 35: Distributor role foyer and corridors provide both

    a physical and optical link with

    the deeper recesses of the

    building.35

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    13

    Photos 36 and 37: The entrance

    area shapes first impressions.

    Harmonious lighting makes for

    a friendly reception.

    Photos 39 and 40:

    Corridor lighting provides

    guidance for visitors and makes

    their route safe. Minimum

    illuminance: 100 lux.

    Photo 38: Light in banisters

    LEDs make it possible.

    38

    37

    40

    39

    36

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    An exhibition may includevideo installations or pre-sentations on large screens

    or monitors of varioussizes. It may also includeaudio exhibits, i.e. record-ings of voices, sounds ormusic.

    Reflected glare isannoyingThe lighting needs to caterfor the use of audiovisualmedia. Because reflectedglare on screens is veryannoying, highly directionallighting should not be in-

    stalled in the vicinity ofmonitors. High luminancefrom neighbouring exhibi-tion areas has the samedazzling effect; stray lightfrom such sources shouldalso be limited.

    For audiovisual presenta-tions, lighting should nor-mally not be too bright neither for visual perceptionnor for the perception ofsounds on which visitors

    need to concentrate. Wherepresentations are interac-tive, however, it is importantthat controls such as but-tons and their labels should

    be easy to identify. The illu-minance of the additionallighting provided for the

    purpose and its radiance inthe direction of the screen(reflected glare) and theoperator (direct glare) mustnevertheless be limited sothat they do not interferewith visitors perception ofthe presentation.

    Computer roomWhere computers andmonitor screens are not in-tegrated in the exhibitionbut installed in a separate

    computer workstation room,it is advisable to light thatroom as if it were an office(see page 19). If the timevisitors spend in the roomis kept short for exampleby putting a limit on themaximum length of stay the lighting concept of theexhibition can also beadopted here even if itmeans a lower lightinglevel. Having said that, therisk of direct and reflected

    glare must always be ruledout.

    Audiovisual media

    14

    Photo 42: In a separate

    computer room, the rules of

    office lighting apply.

    Photo 43: Feeling, hearing,

    seeing all the senses are

    involved in experiencing the

    exhibition.

    Photo 41: Audiovisual media

    can form part of an exhibition.

    Catering for them calls for

    lighting incorporating no highly

    directional light, delivering

    illuminance tailored to

    presentations and providing

    adequate light for the use of

    controls.

    41

    42

    43

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    Virtually every type of eventtakes place in a lectureroom; certain guided toursalso start and end here. The

    room should therefore befurnished and equipped asa multifunctional facility with lighting installations de-signed to create the lightingconditions needed for allthe relevant occasions, thusenhancing concentration,raising receptivity and facili-tating communication.

    Lighting tailored for theoccasionHow flexible the lightingneeds to be depends onthe different lighting situa-tions presented by events.The first requirement is thatluminaires should begrouped on separateswitching circuits becausethe individual lighting situa-tions e.g. reception,lecture or presentation call for different system set-tings. One luminaire groupmay be left switched off,for example, while a sec-ond is activated and a third

    is dimmed.

    The task of lighting control isperformed via a simple con-trol unit or in larger rooms by a lighting managementsystem. With lighting man-agement, programmed light-ing scenes can be adaptedto individual conditions with-out altering the program-ming. Cross-fade times canbe set as required on ascale from one second to

    several minutes. Most light-ing management systemsalso offer the option of incor-porating window darkeningand sunshade settings intoprograms.

    One lighting control systemrecommended for lecturerooms is the DALI system(Digital Addressable Light-ing Interface) with its stan-dardised digital interface.Its key advantages are that

    it has few components,requires little wiring and iseasy to operate.Information is available atwww.dali-ag.org.

    What is always useful insome cases also for lectur-ers is the opportunity to

    control the lighting from aremote device.

    Accent lighting essentialApart from having a func-tional role, lighting is alsoan element of interior de-sign. Accent lighting, for ex-ample, is essential in aprestigious lecture room.Numerous punctual light

    sources, indirect lightingcomponents emphasizingthe architecture of the room

    and planar or directional il-lumination of pictures andwall areas produce anagreeable effect. For thelighting situationreception, general andaccent lighting should beclosely coordinated andprogrammed to be activat-ed together.

    Lecture room

    15

    Photo 45: Lecture room lighting

    is multifunctional lighting

    designed to create tailored

    lighting conditions for different

    situations.

    Photo 44: Film presentation

    and lecture are the two

    lighting situations most

    frequently found.

    44

    45

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    16

    Library lighting has severalfunctions: it helps us getour bearings, helps us findthe literature we require,

    facilitates reading and cre-ates a peaceful to subtlystimulating atmosphere.The basis for planning isDIN EN 12464-1. As ageneral rule, the moredemanding the visual task,the higher the lighting re-quirement. The illuminancerequired for circulatingareas, for example, is 100lux, for shelving systems200 lux. Reading areas,however, call for 500 lux.

    Fast orientationThe general lighting withadditional route markingand identification of exits needs to permit fast orien-tation and provide guid-ance around the rows ofshelves. Direct/indirectlighting produces anagreeably bright ceilingand prevents the so-calledcave effect that can easilyoccur in parts of a library.Where direct lighting com-

    ponents are kept small,annoying reflections(reflected glare) on glossypaper are also reduced.

    Suspended luminaires fortubular fluorescent lampsare the most widely usedhere, along with luminairesfor metal halide lamps inhigh-ceilinged rooms.

    Vertical lightingcomponents

    Bookshelves and bookcas-es should be well illuminat-ed over their entire area.Vertical components needto reach to the lowest shelfto enable titles on bookspines to be read withease from a reasonabledistance. Wallwashers withasymmetrical beams areparticularly suitable for thislighting task. Lamps with agood colour renderingindex (Ra 80) ensure

    that books can be easilyidentified by the colour anddesign of the spine, whichare often used as searchcriteria.

    Reading desks requirebrighter lighting. Wheredesk luminaires are used tosupplement the generallighting, visitors can raisethe lighting level to suittheir personal requirements.

    Library

    Photos 47 and 48: Wallwashers with asymmetrical

    beams illuminate shelves from the ceiling (47)

    or as integrated shelf luminaires (48).

    Photo 46: Helping visitors get

    their bearings, facilitating

    reading, creating a peaceful to

    subtly stimulating atmosphere

    these are the tasks addressed

    by library lighting.

    46

    48

    47

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    17

    Some museums havestudy rooms, which offermore peace and quiet thanreading desks in a library.

    Here, students and otherswith special interests canconsult not only books butalso exhibition and archivedocuments.

    Exacting visual tasksEven if a study room is notequipped with computers,the lighting should cater formonitors because nearlyanyone researching a sub-ject today has a laptop athand. Working at a com-puter, reading and writingare demanding visualtasks, for which DIN EN12464-1 sets out a minimumof 500 lux illuminance. Be-cause glare impairs visualperformance and causesvisual discomfort, careneeds to be taken as inan office or at any otherVDU workplace to ensurethat neither direct norreflected glare occurs.

    Solutions suitable for the

    direct lighting include pen-dant luminaires mountedsingly or in continuousrows with high-gradereflectors and louvers anddownlights with similaroptical control elements.Alternatively, direct/indirectlight can be provided bypendant luminaires orstand-alone luminairesspecifically designed foroffice use.

    Adjustable lighting levelA particularly high degreeof comfort is offered bylighting systems in whichstand-alone luminaires canbe dimmed or supplemen-tary desk-top reading lightsswitched on to tailor thetask lighting level to indi-vidual requirements. Withfluorescent lamps or com-pact fluorescent lampsoperated by (dimmable)electronic ballasts (EBs),

    study room lighting canalso be particularly eco-nomical.

    Study room

    Photo 49: Daylight or artificial

    light enters the study room asindirect light from the light

    wells. Downlights along the

    sides of the room provide

    supplementary lighting.

    Photo 50: The luminaires for

    fluorescent lamps are mounted

    on power track to radiate light

    upwards or downwards.

    They provide indirect and direct

    lighting.

    Photo 51: These desks are used

    mainly by students. 500 lux

    illuminance is provided for

    reading and writing tasks.

    49

    50

    51

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    18

    Cafeterias and museumshops are attractive places,especially at the end of amuseum visit. The culinary

    offerings are welcome andmany people buy themerchandise on sale assouvenirs or gifts.

    Cafeteria lightingFor cafeterias, differentiatedlighting with various room-structuring systems is rec-ommended: e.g. pendantluminaires for tables, wallluminaires and downlightsfor a moderately higherlighting level, downlightsand spots for accent light-ing. Depending on the sizeand design of the cafeteria,a single lighting systemmay be enough.

    The range of design op-tions for catering establish-ment lighting is almostendless. Limits are reachedonly where visual perfor-mance and visual comfortare significantly impaired,which means that glaremust always be avoided.

    Harsh shadows are alsobad because they interferewith facial recognition.

    In terms of brightness, ser-vice areas in a cafeteriacan keep a low profile with one exception: the

    food counter and any otherareas where food and drinkare displayed or on saleneed to be more brightly litthan the rest of the room.DIN EN 12464-1 stipulates200 - 300 lux illuminancehere. This helps guestsget their bearings and facil-itates the visual task ofchoosing food.

    Sales lightingCapturing the attention oftodays visually spoiltconsumer calls for cleverlydesigned sales presenta-tions. The spectrum ofcustomised solutions is aswide as the range ofmodern lamps, luminairesand spots. For a museumshop, the design challengeis to achieve optimal har-mony between the struc-ture and furnishings of theroom and lighting systemsdesigned to suit the mer-chandise on sale.

    A distinction needs to bemade between generallighting viewing light and accent lighting display light for shelves,walls or special offer pre-sentations on the salesfloor. The rule of thumb forthe right mix is: the moreupmarket the range, themore stylish the lightingand the greater the impor-tance attached to differ-

    entiated accent lighting.

    The overall impressionmade by graduated bright-ness levels determineshow stimulating customersfind the sales(room)atmosphere. However, cau-tion is required: excessivedifferences in brightnessplace too much strain onthe eyes of shoppers andstaff. Detailed informationis provided in FGL booklet

    6 (see page 45) onsalesroom and shop win-dow lighting. The relevantstandard is DIN EN123464-1.

    Cafeteria, museum shop

    Photo 53: The scene is

    dominated by the rows of small

    punctual light sources.

    Photo 54: Accentuating light

    with graduated brightness

    levels creates a stimulating

    sales(room) atmosphere.

    Photo 52: The general lighting

    casts a discreet diffuse light.

    52

    53

    54

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    19

    Workplace lighting is need-ed for rooms which arenot open to the public andwhere the lighting caters

    solely for the visual tasksperformed by the peoplewho work there. Theserooms are essentiallyoffices, e.g. administrationareas, workshops andstorage facilities such aswarehouses, depots andarchives.

    Office lightingThe first requirement for vi-sual performance and visualcomfort is an adequate levelof lighting. For compliancewith DIN EN 12464-1, illumi-nance in the task area mustbe no lower than 300 lux.The standard makes adistinction between room-related, task area and worksurface lighting (more infor-mation in FGL booklet 4,see page 45).

    The most popular officelighting solution is basedon pendant luminaires orstandard-alone luminaires

    for direct/indirect lighting,which most people findagreeable. The alternative direct general lightingwith recessed or surface-mounted ceiling luminairesor pendant luminaires withspecular louvers is ap-preciated especially for itsuniformity.

    One of the most importantquality criteria, particularlyfor VDU workplaces in an

    office, is direct and reflect-ed glare limitation byappropriate positioning ofluminaires, desks andmonitors. Where accentlighting is provided by wallluminaires or showcase orpicture lights, care must betaken to ensure that dis-turbing reflected glare isavoided.

    Workshop lightingFor compliance with DIN

    EN 12464-1, what appliesto offices see above basically applies also toworkshops. Regardless ofthe type of work performed,

    the illuminance in museumworkshops, includingtraining workshops, shouldbe 500 lux. The finer and

    more critical the visualtask, the more light isneeded. For this, supple-mentary workplace lumi-naires can be used to raisethe illuminance at theworkpiece. A suitable solu-tion for the general lightingis task lighting with lumi-naires for fluorescentlamps arranged parallelto windows, preferably withlight falling on the work-bench from the side.

    Generally speaking, it isadvisable in workshops toinstall luminaires with ahigher degree of protec-tion. A luminaire protectedto IP 43, for example, isprotected against theingress of solid particles 1 mm and againstspraywater, while an IP 54luminaire is dustproof andprotected against splash-water.

    Storage room lightingThe kind of work done instore rooms, depots orarchives requires less lightthan craft activities. Never-theless, relatively highilluminance is important forhandling small items instorage and for all workinvolving reading tasks(labelling items for storage,completing forms). If thereading and searching taskis focused on shelves i.e.

    a vertical plane as muchas 300 lux vertical illumi-nance may be required.

    Higher illuminance than the100 lux stipulated in DINEN 12464-1 facilitatesreliable visual perception,heightens concentration,helps to avoid mistakesand guards against acci-dents. Luminaires for fluo-rescent lamps are the mostsuitable option for rooms of

    normal height; luminaireswith high-pressure dischargelamps are the solutionrecommended for interiorswith higher ceilings.

    Workplace lighting

    Photo 55: In offices, light must

    cause neither direct glare nor

    reflected glare on screens.

    Photo 56: The finer and more

    critical the visual task, the more

    light is required.

    Photos 57 and 58: Storage

    facilities require a minimum of

    100 lux to be standard-

    compliant; higher illuminance

    levels are better.55

    56

    5857

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    Whether sculptures or in-stallations, some works ofart are intended to beexhibited outdoors whileothers may become candi-dates for outdoor displaybecause of their size. Forthe majority of such ob-jects, an inner courtyard or

    small patch of garden isnormally enough.

    Interplay of light andshadowOutdoor illumination atdusk or at night basicallyhas the same effect as illu-mination with directionallight in an exhibition room(see pages 2, 6). But it alsogives exhibits an appear-

    ance they do not have indaylight: the artificial light-ing creates new structures,reinventing the object in agame of light and shadow.

    The best way to determinethe perfect location for a

    mobile spotlight or flood isto conduct trials withlight from below, from be-low and from the side,from the side, from above,from above and from theside, or even bounced offanother surface. Everysolution has a charm of itsown. For lighting frombelow, recessed groundfloods are the alternative to

    spots. Highly focusedbeams are by far the firstfavourite; with illuminationfrom below and someother configurations, thebeam spread can begreater.

    Avoid glareIf the idea is to illuminatethe whole object, lightsneed to be set at a greaterdistance than for highlight-ing details. When position-ing spots and floods, it isimportant to make surethat observers will not bedazzled, at least in theprincipal viewing direction.

    To achieve the same light-ing impact with differentobjects, the general rule is:the darker the object andbrighter the surroundings,the more light is needed.Ultimately, however, evenilluminance is a matter of

    taste and design intention.

    Outdoor exhibits

    20

    Photo 60: Light from below

    the stationary recessed ground

    floods are installed in groups.

    Photo 61: Facade painting

    floodlighting creates a splash of

    colour at night.

    Open air museumOpen air museums area showcase for historicalbuildings and complex-es, either in their originalstate or reconstructed.They close when it isdark, so artificial lighting

    is generally installedonly inside the buildings if possible withoutspoiling the impressionof a time before the ad-vent of electricity. Wherean open air museumstays open after dark,path lighting is alsorequired.

    Photo 59: The interplay of light

    and shadow casts sculptures in

    a dramatic light

    59

    6160

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    Buildings bathed in lightimpact at night because oftheir architecture. Wherefacade lighting makes this

    visible, decorative nightimages are created. Illumi-nated advertising signsand frontal floodlightingalso help shape a museumbuildings night-timeappearance.

    Facade lightingLight can make any build-ing an eye-catcher.Combined with fascinatingarchitecture, well-plannedfacade lighting imbues abuilding with a uniquequality and enhances thearea around it at the sametime.

    Illuminating the entirebuilding has a long-rangeimpact; harnessing lightto emphasize only architec-tural details heightens itspresence for passers-by.Where the principal view-ing direction and the direc-tion of illumination are notidentical, light-dark con-

    trasts create a three-dimen-sional effect: an angle ofaround 60 degrees to theviewing direction is right forplain or fairly plain facades;for more detailed or ornatefacades, the angle can besmaller.

    Ensuring floodlights are notinstalled too close to thebuilding avoids excessivelydeep shadows. Beamsshould not cross or shad-

    ows will be too light.

    Floods with a long-rangeimpact should be posi-tioned high and mountedas inconspicuously aspossible. High-pressuresodium vapour lamps un-derline the character ofwarm colours and materi-als; for cooler-lookingsurfaces, metal halidelamps are a suitable solu-tion. Illumination is also

    possible with wall lumi-naires integrated in thefacade and recessedground floods positioneddirectly in front of it.

    The illuminance required isdetermined by the colourand thus reflectance of theilluminated building (build-ing luminance) and by theambient brightness: thedarker the building andbrighter the surroundings,the more light is needed.Precise planning avoidslight emission into the sur-rounding area.

    Alternatives to classicalillumination are presentedby fibre-optic lighting sys-tems and LEDs, with whichfacades or parts of facadescan be bathed in dynamicchanging coloured light.Another possibility isfacade design based onactivated (and controlled)interior lighting.

    Other forms ofillumination

    Facade lighting is normallya discrete design element.However, illuminated sig-nage e.g. the name of themuseum in luminous letters needs to be plannedto suit it. To achieve the de-sired effect, any additionalsignal lighting, such asfloodlighting for flags orbanners, needs to be coor-dinated with the facadelighting.

    In other outdoor areas, at-tractive scenes are alsocreated by illuminatingtrees or other vegetation.The rules to be followedhere are the same as foroutdoor feature lighting(see page 20). If the facadeis also illuminated, lightsshould only be trained onplants well away from thebuilding.

    Night scenes

    21

    Photos 62 and 63: Light turns

    facades into eye-catchers,

    enhances the building and

    gives it a unique quality.

    Photo 64: The LED semicircleon the facade of the Buhlsche

    Mhle event centre in Ettlingen

    symbolises the millwheels that

    turned here in the past.

    62

    63

    64

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    22

    Interior lighting with daylightis an architectural chal-lenge that absolutely mustbe addressed and resolved

    at the early design stage ofa new building. Conditionsfor harnessing daylightcan rarely be created laterand system modification isdifficult. Daylight planningis a matter for experiencedprofessionals.

    Daylight museumPublic museums built in thefirst half of the 19th centuryhad to rely on daylight.From early times, architectsincorporated skylights toharness it: in 1789, the sidewindows of the SalonCare at the Louvre in Pariswere bricked up to enableall the wall to be used forexhibits.

    For a long time, despitethe availability of artificiallighting, every new museumwas built as a daylit facility.But that changed in the1950s and 60s when itwas realised how much

    damage daylight can do,especially to paint andother organic materials. Forsome time after that, allnew museums were builtwith rooms without win-dows.

    Today, our knowledge oflighting engineering cou-pled with modern controland regulation technologymakes it possible fordaylight to be precisely di-

    rected and dosed. So onceagain daylight plays amajor role in museum con-struction and design.

    SkylightsSkylights are classic day-lighting elements for picturegalleries. They provide uni-form, diffuse lighting. Be-cause the light is admittedover a large area, the shad-ows produced are soft.The incident daylight that

    passes through a skylightreaches nearly every part ofthe room, including free-standing display cabinets,sculptures and partitions.

    Because no windows arepresent, more wall space isavailable for paintings.There is also no problemwith reflections on exhibi-tion walls due to incidentdaylight from the side.

    With large skylights, unwel-

    come interference mayoccur and needs to betackled by positioning theskylights appropriately andproviding for precise opti-cal control. There is a risk,for example, of light being

    unevenly distributed overthe walls. In rooms withdark furnishings, in particu-lar, the vertical illuminanceat eye level is often too

    low. The contrast betweenwall and ceiling brightnesscan cause glare. And evenwith light incidence fromabove, reflections can

    sometimes occur on pic-tures on the wall.

    Direct sunlight must alwaysbe locked out. But lightprotection is not alone inpresenting high require-ments: what all modernskylight solutions have in

    common is that they areexpensive to design andconstruct for daylight direc-tion, control and filtering.The use of skylights to har-ness daylight is confined tothe upper storeys of a

    building or calls for single-storey design. Skylights areno substitute for the visualcontact with the outsideworld provided by windows.

    WindowsOutsized windows are notnecessarily a suitable alter-native to skylights and not

    actually the right tool formaking maximum use of

    daylight. On the otherhand, there are many waystoday to direct daylight andlock out direct sunlighteven in rooms with lateralwindows. Having said that,these non-transparentsystems do not fulfil therequirement met by day-light museum windows inmaking diurnal and sea-sonal change as well asthe vicissitudes of theweather a visual experi-

    ence.

    Windows reduce theamount of wall space forexhibits. Undirected andunfiltered incident daylightcan give rise to reflectionson exhibition walls.

    Daylight and artificiallightIf daylight and artificial lightare mixed, their raysshould be fully blended be-

    fore they fall on an exhibit.This also means that thespatial distribution of thetwo types of light needs tobe coordinated. The rea-

    Daylight

    Daylight has considerable damage potentialBoth daylight and artificial light contain rays which maycause exhibits to fade, dry out or become discolouredor deformed if exposed to the light for long periods.But daylight is certainly the more dangerous. This is

    confirmed in the art history publication ber das Lichtin der Malerei (Wolfgang Schne, Berlin 1993), which,when considering light sources, focuses almost exclu-sively on daylight. Few pages are devoted to artificiallighting.Information on light protection is found in this bookleton pages 30 ff.

    Photo 65: The camera looks

    behind the luminous ceiling of

    an exhibition room where

    daylight and artificial light are

    mixed as required.

    65

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    23

    Daylight incidence from abovethrough a luminous ceiling(prin-ciple in cross-section of room)

    With light from above, more fallson horizontal surfaces in themiddle of the room than onsurfaces at the edge and always(angle) more than

    on vertical surfaces in thesame place, on walls more thanon free-standing partitions.

    Daylight incidence from the sidethrough a window(principle incross-section of room)

    With light from the side, the furtherit has to travel from the windowwall, the lower the illuminance onboth horizontal surfaces

    and vertical ones, although ver-tical surfaces are better illuminatedbecause of the more favourableangle of incidence.

    Photos 66 + 67: The luminous ceiling of the 800 m Salle des

    Etats of the Louvre in Paris has an area of 300 square metres. It

    directs the incident daylight that passes through a glass roof into

    the exhibition room. Supplementary artificial lighting is activated

    when the monitoring system reports there is no longer enough

    daylight. 360 luminaires, each fitted with two 80 W fluorescent

    lamps, are installed, some with wide-angle and some with narrow-

    angle reflectors. Illuminance is 250 lux on the floor of the museum,

    100 lux at the walls. Photo 67 shows the inside of the ceiling

    construction.

    sons: the lamps used forartificial lighting radiatelight of particular colours,while the spectral composi-tion of daylight changes allthe time. In addition, thetwo have different angles ofincidence and differentbeam angles. This gives

    rise to conflict; the appear-ance of exhibits is distortedif the two light forms arenot fully blended. The onlyalternative to blending issegregation. This meanskeeping the daylit zoneand the zone illuminatedby artificial light far enoughapart to ensure that the

    two types of light do notinterfere with one another unless the twilight is delib-erately used to create aparticular atmosphere inthe room.

    Photo 68: The daylight entering

    through the skylights falls main-

    ly on the exhibits on the upper

    floor; the corridor needs

    supplementary lighting.

    66 67

    Abb. 10-15

    68

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    24

    At its most sophisticated,lighting managementmeans automation of light-ing systems. Lighting man-

    agement encompasses allsystems which go beyondmere on/off control sys-tems which control andregulate lighting by re-sponding to variance fromsetpoint values.

    Degrees of automationLighting management sys-tem components, whichcan be used alone or incombination with others fordifferent degrees of au-tomation, include:

    retrievable pre-pro-grammed lighting scenes motion detectors primedto activate lighting inresponse to movement(presence-dependentlighting control) daylight-dependentlighting level regulation bydimming and/or partial deactivation in re-

    sponse to signals from light sensors in the

    room or exterior light sensors.

    The control and regulationcomponents of a lightingmanagement system areintegrated in luminairesand operator interfaces.They may be programmedto govern individual lumi-naires, individual rooms orgroups of rooms or theycan be wired into the build-ing management system

    (BMS).

    Lighting management sys-tems can be realised withthe standardised digital in-terface DALI (Digital Ad-dressable Lighting Inter-face). This also permits in-tegration in building man-agement systems such asBUS systems. Information:www.dali-ag.org.

    Lighting management inmuseumsThere are numerous waysin which lighting manage-

    ment can be used in amuseum:

    Lighting managementsystems can activate anddeactivate or dim theartificial lighting in responseto changes in availabledaylight. They can be used toprovide daylight-dependentcontrol for sun-screens andanti-glare shielding onskylights or windows. Lighting managementsystems facilitate lightingproductions: stage lightingor dynamic effects caneasily be programmed. Lighting managementcan be used to set differentilluminance levels in differ-ent zones: individual lumi-naires are simply dimmed.This is useful for casting anexhibition in a dramaticlight or as a light protectionmeasure for individualexhibits. Lighting managementfacilitates simple multifunc-tional use of individualinteriors. Lighting managementenables installed lumi-naires to be assigned todedicated exhibition lumi-naires without de-installingthe existing luminairesand without the need forre-wiring. A lighting managementsystem can monitor lumi-

    naires and report theirfunctional status or failure. Lighting managementsystems can log the oper-ating status of the lightinginstallation and thus recordthe radiant exposure of theexhibits for the light pass(see page 32). Emergency lighting caneasily be integrated into alighting management sys-tem. A lighting installation

    controlled by a lightingmanagement system con-sumes less energy than anon-managed installation.

    Lighting management

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    Photo 73: Digitally controlled

    daylight ceiling the steplessly

    variable artificial lighting is

    added as required.

    25

    Photos 71 and 72: The lighting in this exhibition and event hall

    permits a variety of room uses. The lighting situations shown here

    controlled by a lighting management system are bright

    daylight-white lighting (71), which is normally used during the day ,

    and less bright warm-white lighting (72), intended mainly for

    evenings.

    Photos 69 and 70: A lighting

    management system enables

    the separately switched

    luminaires and luminaire groups

    to be easily controlled. The 3D

    presentation in photo 69 showsthe lighting situation fully

    activated, photo 70 shows the

    spot lighting situation.

    69

    70

    71

    72

    73

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    26

    Over 80 percent of all theinformation we receive ispicked up by our eyes.Anyone who studies theconditions needed for see-ing well, i.e. anyone whoknows the basic visualrequirements, understandsmore easily how lightmakes visual performancepossible and what caninterfere with that perform-ance. More detailed infor-

    mation about the basics oflighting is contained inbooklet 1 Lighting with arti-ficial light (see page 45).

    IlluminanceIlluminance (symbol: E)has a major bearing on thespeed, reliability and easewith which we perceiveand perform a visual task.Measured in lux (lx), it indi-cates the amount of lumi-nous flux from a light

    source that falls on a givensurface: where an area of1 square metre is uniformlyilluminated by 1 lumenof luminous flux, the illumi-nance is 1 lux. Example:the flame of an ordinarycandle generates approx1 lux at a distance of1 metre.

    Illuminance is measured onhorizontal and vertical sur-faces. Uniform distribution

    of brightness facilitates thevisual task.

    In exhibition rooms, thelevel of illuminance is often

    determined first and fore-most by the sensitivity ofthe exhibits. For endan-gered artworks, for exam-ple, the illuminance shouldbe as low as possible (lightprotection, see page 30).

    The second criterion is de-sign intention. And in thirdplace exceptionally isthe question of how muchlight is needed to enable

    the visual task to be per-formed. Applying all threecriteria produces a consen-sus on the illuminance levelrequired, although it needsto be realised that the levelmust not be too low.

    The average illuminancenormally provided in exhi-bition rooms ranges from150 to 250 lux, dependingon whether the lightingcaters for wall-mounted ex-

    hibits or exhibits throughoutthe room, with higher verti-cal components or morehorizontal ones. Sometimesit needs to be darker forconservation reasons;brighter lighting is oftenonly required to offset day-light incidence.

    Where lots of diffuse andnot much directional light-ing is used, the exhibitionroom is illuminated more

    uniformly. Light directedexclusively onto exhibitsresults in a largely unevenpattern of illuminance inthe room.

    Luminance distributionLuminance (symbol: L) isthe brightness of a lumi-nous or illuminated surfaceas perceived by the humaneye and is measured incandelas per unit area(cd/m ). Luminance distrib-ution in the visual field hasa crucial bearing on visualperformance because itdefines the state of adapta-tion of the eye. The higher

    the luminance, the betterthe visual acuity, contrastsensitivity and performanceof ocular functions.

    For visual tasks at a desk,concentration is promotedby brighter areas in thecentre of the visual field.In the context of an exhibi-tion, this means that ex-hibits should always havea higher luminance thantheir surroundings. One

    way to achieve this is withgraduated brightnesslevels.

    Visual comfort is impairedwhere luminance is too lowor differences in luminanceare too slight (disagreeablelighting atmosphere),where differences in lumi-nance are too marked(eyes become fatigued be-cause of the constant needto re-adapt) and where

    points of luminance are toohigh (glare).

    Seeing, identifying, perceiving

    Photo 74: The diffuse light

    provided by the luminous

    ceiling is combined here with

    directional spotlighting.

    Fig. 16 74

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    L

    EX

    IC

    ON

    27

    AdaptationAdaptation to differ-ences in brightness is

    performed in the hu-man eye by receptorson the retina andchanges in the size ofthe pupil. Adaptationfrom dark to light takesonly seconds; fulladaptation to darknesstakes minutes.

    The state of adaptationaffects visual perfor-mance at any moment:the more light is avail-able, the faster efficientvisual performance canbe restored. Visual im-pairment occurs wherethe eye cannot adaptto differences in bright-ness fast enough.

    LampNo lamp, no light: theterm ,lamp refers to anengineered artificiallight source such as anincandescent lamp, flu-

    orescent lamp, etc..

    LuminaireThe term luminairerefers to the entireelectric light fitting, in-cluding all the compo-nents needed to mountand operate the lamp.Luminaires protectlamps, distribute theirlight and prevent themcausing glare.

    Photo 75: The room is relatively

    dark, the higher illuminance

    at the artworks makes the visual

    task possible. Low illuminance

    is sometimes necessary in

    this context to protect exhibits

    from light.

    Photo 76: The diffuse lightfrom a luminous ceiling works

    only if it is bright. The

    illuminance here is close to

    250 lux.76

    75

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    28

    Direct glare,reflected glareDirect glare is caused byluminaires, general-diffuse

    lamps or other excessivelyluminous surfaces includ-ing windows. Reflectedglare is caused by reflec-tions on shiny surfaces.

    Glare can interfere withvisual performance to suchan extent that reliable per-ception and identificationbecome impossible. Physi-ological glare is a measur-able loss of visual functionssuch as visual acuity.Psychological glare causesdiscomfort and loss of con-centration. Glare cannotbe eliminated altogetherbut it can be significantlyreduced. There are recog-nised methods for assess-ing both types of glare.

    In exhibition rooms, reflect-ed glare can be used to alimited extent as a designtool for example whereshiny exhibits with brilliantlyreflective surfaces are

    bathed in dramatic direc-tional light to maximisetheir impact.

    Direction of light andmodellingShapes and surfaces in theroom need to be clearly(visual performance) andcomfortably (visual com-fort) identifiable. This callsfor balanced, soft-edgedshadowing. Shadow forma-tion depends on the direc-

    tion of light, which is itselfdetermined by the distribu-tion and arrangement of lu-minaires in the room. Useof light and shadow in ex-

    Seeing, identifying, perceiving

    hibition rooms is describedin this booklet on pages2 ff.

    Visual performance andvisual comfort are alsoaffected by the light colour

    Photos 7779: Museum lighting

    has to meet special standards.

    At 150 to 250 lux, it does not

    need to be very bright but

    every effort should be made toensure it does not cause glare

    because both direct and reflect-

    ed glare interfere unacceptably

    with the visual task.

    and colour rendering prop-erties of the lamps used.These two qualities areexplained on page 35.

    77

    78

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    29

    L

    EX

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    ON

    Luminous intensityLuminous intensity

    (symbol: I) is theamount of luminousflux a reflector lamp orluminaire radiates. It ismeasured in candelas(cd). Plotting the lumi-nous intensity values atthe different emissionangles on a graph pro-duces an intensity dis-tribution curve (IDC).

    ReflectanceReflectance indicatesthe percentage of lumi-nous flux reflected by asurface. The reflect-ance of light-colouredsurfaces is high, that ofdark surfaces low. Thismeans that the darkerthe room furnishings,the more light is need-ed to create the samebrightness.

    Visual taskVisual tasks are de-fined by light/dark and

    colour contrasts as wellas by the size of de-tails. The more difficultthe visual task, thehigher the lighting levelneeds to be to permitthe visual performancerequired.

    Visual performanceVisual performance isdetermined by the vi-sual acuity of the eyeand its sensitivity to dif-

    ferences in brightnessand darkness as wellas by speed of percep-tion.

    79

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    30

    Fading, yellowing, darken-ing, discolouring, twisting,bending, splintering, tear-ing, swelling, shrivelling,

    shrinking, dissolving itsounds like a dire list ofconsequences. In actualfact, exhibits displayed indaylight or under artificiallighting are not normallyexposed to more than oneof these hazards.

    Optical radiationEven so, the hazard poten-tial should not be underes-timated. It exists becausesome materials cannottolerate optical radiation,which includes short-waveultraviolet (UV) radiation(100380 nm = nanome-tres ), light in the visiblerange (wavelengths of380780 nm) and long-wave infrared (IR) radiation(780 nm to 1 millimetre).It triggers photochemical orthermodynamic (physical)processes. Daylight, withits high UV content and thethermal radiation of thesun, is always critical.

    Lighting technologists andother scientists have stud-ied these phenomena. Aswell as empirical evidenceand tips on light protectionfor conservation, that re-search has furnished a setof formulas that make theharmful effects calculablebut no more comprehensi-ble for the non-engineer.So formulas, mathematicalrelationships and computa-

    tions will not be looked athere.

    The important thing toknow is that the damage isdone not by the radiationthat strikes the object butby the rays it absorbs. UVradiation and short-wavelight are generally moreharmful than long-wavelight and IR radiation.Which means radiation inthe visible spectrum i.e.

    light can do damage.

    PhotochemicalreactionsOrganic materials in partic-ular are susceptible tophotochemical change.Inorganic material is muchless often affected. Inmuseums, the greatest fearis of changes in colour,i.e. fading, yellowing ordarkening of paper, fabrics,wood or the colour pig-

    ments, binders or varnish-es used in watercolour andoil painting.

    Photochemical change is aslow process. But lightdamage is cumulative andirreversible: no materialever forgets radiation or thelength and intensity of ex-posure to it.

    The most important para-meters contributing to pho-

    tochemical processes are:

    Irradianceof the object. Irradiance isindicated by the symbol Eeand is measured in W/m Irradiation timeis the length of time an ob-ject is exposed to irradia-tion. Irradiation (He) is theproduct of irradiance andthe length of exposure to it.The higher the irradianceand longer the exposure,

    the greater the potentialrisk.

    Spectral radiation distri-bution of the light source(daylight or lamps)Light of a particular wave-length has a particularspectral colour. White lightis made up of a large num-ber of spectral colours ofdifferent intensity. Thisspectral radiation distribu-tion is characteristic of eachlamp type as well as day-

    light. Incandescent lamps,for example, produce alight dominated by the redsof the long-wave spectralregion; daylight, on the oth-er hand, is dominated bythe short-wave blues. Relative spectralsensitivityindicates the dependenceof an objects light sensitivi-ty on the wavelengths ofthe reference radiation. Effective threshold

    irradiationis the measure of the ab-solute sensitivity of an ob-ject. Change starts to occurin light-sensitive materialson first exposure to radia-tion - at first invisibly, thenwith visible signs. Thethreshold at which visibledamage starts to be doneis the yardstick used for as-sessing light sensitivity.

    The threshold irradiation

    time (i.e. the time till thethreshold is reached) isshown for individual materi-als under daylight or thelight of different lamps.

    Effective irradiationis ascertained mathemati-cally from the values foroptical radiation (spectraldistribution), irradiation andrelative sensitivity of theobject.

    The following character-istics and conditions alsoplay a role in photochemi-cal processes: spectral absorption char-acteristics of the materialand its specific dispositionfor secondary reactions, ambient and objecttemperature, moisture content of theobject and its surroundings, pollutants or dustdeposited on the object, characteristics of thecolouring agents and pig-ments used.

    Damage potentialThe damaging irradianceand the illuminance at theexhibit stand in a fixedratio to one another. Thatratio indicates the damagepotential. It is the crucialquantity used to describethe damage that can bedone in a lighting situationwhere particular lightsources and filters aretrained on particular ex-hibits and materials.

    Light protection

    80 81

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    31

    Pre-exposure to lightStudies show that pre-exposure to light can alsoplay a role in the selectionof lighting for an exhibit.Even small doses of aneffective irradiation damageobjects which have neverbeen exhibited or pre-exposed to light, whereas ittakes much higher dosesto cause the same damage

    to older, pre-exposedmaterial that has alreadyundergone change.

    Many molecular degrada-tion processes graduallyslow down and finally evencome to a halt. In thesecases, it is possible to takeaccount of the pre-expo-sure time and reduce thelight protection measuresaccordingly. Pre-exposureto light is best established if

    all irradiation times (andtypes) are documented. Toestablish pre-exposure bycomparison measurements,parts of the object mustbe unexposed.

    Measures guardingagainst photochemicalchangeWhere photochemicalprocesses need to be pre-vented from occurring inthe first place, or at least

    slowed down, light protec-tion means reducing the ef-fective irradiation. In partic-ular, exposure to highlydamaging radiation in the

    short-wave region espe-cially UV radiation needsto be reduced or ruled outaltogether.

    There are a number ofeffective ways to do this: Choosing a suitable lightsource: very sensitive mate-rials should be illuminatedwith light that has lessdamage potential. Filtering out harmfulradiation: if other lamps areto be used or radiationexcluded altogether, short-wave radiation can beblocked by filters.

    Halogen lamps for line andlow voltage are availablewith integrated UV blockersbut this is not enough tomeet conservation require-ments. The only tools ofchoice here are special

    filters. Limiting exposure: indarkness, the risk of photo-chemical change is reduc-ed to zero.

    Filtering to 420 nmGlass filters, absorptionfilters, dichroitic filters, plas-tic lenses or foils therange is wide, appropriatefilters are available forevery application. They canbe used to cut off short-

    wave radiation up to380 nm. Where filters alsoeliminate light in the short-wave region the cut-offwavelength is 420 nm. If

    82

    other wavelengths arefiltered out, the spectraltransmittance shifts so farthat the colour renderingindex sharply deteriorates.An alternative to light exitfilters is showcase glass orpicture glass that filters outUV light. Using it in additionto other light protectionmeasures, however, doesnot make for better conser-

    vation conditions.

    Limited irradiation timeWhere possible, exhibitsand exhibition roomsshould only be illuminatedfor a short time. Outsideopening hours, darkness isbest. For cleaning opera-tions or for setting-up,dismantling and repairwork, separate, non-dam-aging lighting is recom-mended; presentation

    lighting, at least, should notbe switched on for suchoperations and the generallighting should bedimmed.

    In many cases, presencesensors are a useful toolfor limiting irradiation dur-ing opening hours. Timelydimming makes for visuallyagreeable dark/light transi-tions. Care should be takento ensure a long-enough

    delay before programmeddeactivation.

    DaylightLight protection alsomeans limiting daylightilluminance. For sensitiveexhibits, UV radiation andshort-wave light also needto be filtered out. Assess-ment of the conservation-relevant characteristics ofdaylight is normally basedon the average sky condi-tion with a colour tempera-

    ture of 6,500 K and itsspecific spectral radiationdistribution. Referencingthis standard light type(D65) also makes it possi-ble to establish degreesof damage potential.

    ThermodynamicprocessesThermodynamic processesare almost entirely confinedto organic materials: wood,textile fibres, parchment

    and leather are commonexamples. The thermalload on the exhibit occursas a result of light and IRradiation being absorbedand mostly gives rise todrying processes. Thesereduce tensile strength,elasticity and volume inducing mechanicalstresses which cause firstthe surface, then often theentire object to becomedeformed.

    The physical changes in-duced by heat radiation aremore serious when photo-chemical processes occur

    Photos 80 and 81: The two

    samples were taken from the

    same bolt of fabric. The piece in

    photo 80 was stored out of the

    light and thus screened fromultraviolet rays. The piece in

    photo 81 was exposed during

    the day to sunlight and thus

    also UV radiation.

    Photo 82: Testing colour

    fastness. An experimental set-

    up by lighting technologists at

    Berlins Technical University: the

    irradiated samples 1 and 3 are

    textiles, the rest watercolours.

    Light protection in 1905To protect exhibits from the impact of light, a zoo-logical museum took the radical step of opening

    its exhibition rooms on two days a week for 2hours. During that time the interiors are flooded withlight; at all other times, however, curtains admittingno light whatsoever are drawn across the windows,producing the total blackness found in a photographers dark room.

    An ethnological exhibition went even further: particularly light-sensitive objects like the extremelyprecious coats of feathers [] are protected bykeeping them in containers furnished with curtainswhich visitors can draw back to view the exhibitsinside.

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    at the same time. These areaccelerated by the heatand interact with thermody-namic processes. Physical

    change is also acceleratedby fluctuations in tempera-ture and humidity e.g.due to the activation anddeactivation of lamps.

    Unlike the molecularchange that takes place inphotochemical processes,which can come to a halt,the thermal load on anobject during irradiation isalways harmful.

    The thermodynamic impactof radiation is determinedby the thermal load on theobject and the spectralirradiance, the radiationabsorbed playing a partic-ularly key role. For thethermal load on an exhibi-tion room, the key deter-minant is the product of theluminous efficacy of thelamps and the coefficientof utilisation of the lightinginstallation.

    Protective measuresagainst thermodynamicprocessesThe protective measurestaken against heat loadingcorrespond to thoseagainst photochemicalprocesses. The most effec-tive are:

    Choosing appropriatelight sources: for heat-sensitive materials, the onlysuitable lamps are ones

    32

    Light protection

    Light passThe only way to buildup an accurate pictureof the exposure historyof an object is torecord exposures in alight pass. Data thatneeds to be notedincludes details of pe-riods on display aswell as the type of light

    source used, theilluminance and theirradiation time.

    The relative spectral sensitivity of the materials shown here

    is based on the impact on oil paintings (reference value:

    100 percent). So watercolours, at 485 percent, are nearly five

    times more at risk than an oil painting. The illuminance on

    the object is 200 lux a compromise between the brightness

    needed for the visual task and the conditions required for

    conservation; the illuminance on very sensitive objects should

    not exceed 50 lux.

    The relative damage potential of daylight and the lamps listed

    here is based on the impact of unfiltered light from low-voltage

    halogen lamps (reference value: 100 percent). An object

    exposed to the light of a metal halide lamp with a 380 nm edge

    filter for 1,000 hours at 200 lux illuminance, for example,

    sustains nearly twice as much damage (180 %) as a similar

    object exposed to an unfiltered low-voltage halogen lamp.

    Conversely, this means: for the same degree of damage, the

    object can be illuminated by the unfiltered light of a low-voltagehalogen lamp for nearly twice as long or nearly twice as

    intensely as by the filtered light of a metal halide lamp.

    that emit light with a lowIR content. Where low-voltage halogen lamps areused, cool-beam reflector

    lamps are the right choice.No IR radiation is con-tained in the beams offibre-optic lighting systemsor LEDs. Using IR filters to cut offharmful radiation Limiting exposure Dissipating the heat.Even with lamps that pro-duce a luminous flux with alow heat content, lumi-naires and their immediatesurroundings can heat up.This is possible in a dis-play cabinet, for example.To ensure this secondaryIR radiation does nodamage, it needs to bedissipated. If necessary,fans can be installed toincrease air circulation. The IR radiation of day-light is just as damaging asthat of lamps. So directsunlight always needs to belocked out.

    Relative spectral sensitivity

    Group Material samples in %

    sensitive oil paints on canvas 100

    verytextile samples 300

    sensitive watercolour paints onhand-made paper 485

    Relative damage potential of light sources

    edge filterLight source without

    filter edge at (nm)window glass

    380 400 420 simple double

    in %

    Daylight 235 155 130 110 205 190

    General serv- 85 75 70 65 80 75

    ice tungstenfilament lamp

    LV halogen 100 80 75 70 90 90lamp

    High 220 175 145 110 210 210pressuremetal halidelamp

    Fluorescent 100 85 80 70 95 90lamp,neutral white

    Fluorescent 90 75 70 60 85 85lamp,warm white

    LED, 80 80 80 75 80 80cold white

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    As lamps, luminaires androom surfaces age and be-come soiled, illuminancedecreases. So every light-

    ing installation requiresregular maintenance. Thevalues set out in Europeanlighting standards such asDIN EN 12464-1 e.g. forilluminance are main-tained values, i.e. valuesbelow which the relevantlighting quantity must notfall at any time.

    Installed values shouldbe higherTo ensure the requiredlighting level over an ap-propriate period of timeand to enable the lightingsystem to be operatedlonger without additionalmaintenance work, in-stalled values need to behigher. How much higher isdetermined by applying amaintenance factor.

    Maintenance factors de-pend on operating condi-tions as well as on the typeof lamps, electrical gear

    and luminaires used. Theyneed to be defined andrecorded b