10-84 I E S LIGHTING HANDBOOK

factory visual adaptation as the visitor steps into the lobby from out-of-doors (from an illumination level approaching 10,000 footcandles indirect sunlight). This necessity for adaptation combined with the ad-vertising value of higher levels and brighter surroundings has led many,building designers to provide higher levels of illumination (20 footcandles)

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In hallways and corridors of ordinary ceiling height (less than 30 feet)luminaires should be spaced not more than 20 feet apart. No branchcorridor should be without a luminaire. A luminaire located at a maincorridor junction will serve two branches not more than 10 feet deep. Forsafety in such locations, at least two lamps should be used in each luminaire.No entrance to an elevator or a stair well should be more than 10 feet

from a luminaire. The recommended average illumination level forelevators, and stair wells, is 10 footcandles, assuming high-reflectance sur-faces. The lumieaire and layout should provide such a uniform level thatthe maximum value at any place in the room is not greater than three timesthe minimum.

Theaters

Theater-lighting design begins outdoors with the combination decorativefacade with display cases which identifies the entrance. Part of this en-trance is the marquee. Sources in the marquee often provide a high il-lumination level around the box office. This level is reduced along thetraffic lane into the threater so that the theatergoer's eyes may becomeadapted gradually to the lower levels inside.

Theater lobbies are passageways between the street and the foyer. Anillumination level of 20 footcandles is desirable in lobbies. The walls andceilings should have a high brightness (up to 50 footlamberts) . At signsannouncing current or coming attractions 20 to 40 footcandles should beprovided by local lighting for accent. The luminaires may be ceiling-mounted spotlights, or lamps and reflectors attached to the signboard.

Foyers are areas where traffic is distributed into the auditorium. Anillumination level of 10 footcandles is recommended. This is sufficientfor recognition of acquaintances, for safe movement, and to arouse interestin the decoration, and yet permits quick adaptation to the lower audi-torium level. In larger theaters, a lounge or promenade may separatethe lobby and the foyer. The illumination level in such an area shouldfall between those of the lobby and the foyer.

In the auditorium proper, three rules should be observed: (1) bright-nesses should be low; (2) sources should be placed out of the normal fieldof view from any seat in the house; (3) in motion-picture theaters thelight should be so controlled that a minimum falls upon the screen. (SeeFig. 10-59.) Stray light reduces contrasts in the screen image. Brightnessup to 10 footlamberts may be used between the acts. Luminaires shouldbe located as far outside the field of view as practicable. See also Sec-tion 14.To relieve brightness contrasts between the screen and its immediate

surround and thus contribute to eye comfort, a low brightness of approxi-

INTERIOR LIGHTING 10-85

FIG. 10-59. A community theater auditorium.

mately 1 footlambert on the surfaces adjacent to the screen is recommended.In lighting such surfaces, the source must be concealed and so directed thatno light spills on the screen to reduce picture clarity. Any luminaire typemay be used (coves, shielded downlights, or masked projectors) that willborder the picture screen with surfaces of about one-tenth screen brightness.

For motion-picture theaters, illumination levels can be graded from \footcandle at the rear of the auditorium to y^ footcandle at the front.Some provision should be made to supply higher levels for emergencies,for cleaning, and at the end of the final presentation.Few theaters have sufficient illumination for program reading. In

community theaters where the auditorium may be used for other thanmotion-picture projection additional lighting may be necessary. Theatersused solely for stage plays need not have over-all low-intensity lighting.A minimum of 5 footcandles should be provided everywhere for the read-ing of programs during intermissions. Individually controlled local lumi-naires on the backs of seats have been used successfully in some theatersto provide light for reading programs and for locating lost objects.

Aisle lights located under the outside row of seats can provide usefulillumination without introducing high brightnesses in the field of view ofthe seated audience.Some use is made of carpets impregnated with fluorescent materials

which become luminous when irradiated by means of ultraviolet sources.

Theater Stages

The stage provides the most interesting lighting problem in the theater.Even those theaters designed exclusively for motion pictures occasionallymay accommodate stage shows for charity, for community rallies, andso forth.

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Stage lighting equipment includes border lights, footlights, spotlights,floodlights, and cyclorama floodlights. (See Fig. 10-60.)

10-86 I E S LIGHTING HANDBOOK

FIG. 10-60. Typical plan and elevation for a large stage.

INTERIOR LIGHTING 10-87

FIG. 10-61. Stage-lighting equipment; a. border lights; b. footlights; c. spotlightsand flood lights.

Border lights provide general illumination for the stage. Dependingon stage depth, one to four rows are hung parallel to the curtain, with thefirst border as close behind the curtain as feasible. All border lights aremounted so that they may be adjusted vertically, since otherwise theymight interfere with the use or placement of various stage sets, or not be ina position to supply the proper light distribution. Border lights includebare lamps in long troughs, individual lamps and reflectors grouped to-gether as troughs, and individual, separately operated spotlights. (SeeFig. 10-61a.) In any case color flexibility is a requirement. Bare lampswith different filter coatings; individual reflectors with glass roundels orgelatin filters; and spotlights with gelatin filters are the primary colormediums. Usually three to five colors are used. All those of one colorare wired for simultaneous control. They should be so spaced that uni-form coverage may be provided with any combination. Borders are elec-trically controlled so that each circuit may be dimmed. The incandescentlamps used include 40- to 60-watt bare lamps on 5- or 6-inch centers, 100-to 200-watt lamps in individual reflectors on 9- to 12-inch centers, and 250-to 500-watt lamps in spotlights.

Footlights are located in front of the curtain line and usually consistof one row of sectionalized disappearing units. (See Fig. 10-61b.) Theirpurpose is to soften and eliminate harsh shadows which tend to appear onfaces lighted only from above, and to provide illumination when the stageaction requires the actors to move "downstage" near and beyond thecurtain line. Like border lights, they may be bare lamps in troughs or inindividual reflectors. Usually they are wired in several circuits, and aredimmer controlled,

10-88 I E S LIGHTING HANDBOOK

Spotlights and floodlights located in the wings adjacent to the borderlights or in the auditorium proper provide accent lighting. (See Fig.10-61c.) Many stage designers use spotlights almost exclusively to pro-duce the required high levels, using border lights and footlights to providea more uniform level than may be obtained with the imperfect spotlightoverlap. A spotlight is a luminaire in which a reflector behind the lampor sometimes a lens in front of it, or both, is used to focus the output ofthe lamp in a narrow beam. Incandescent lamps with ratings between 250and 2,000 watts and carbon arcs are used in spotlights. By comparison,floodlights have a wide beam. Lamps of any type and size are used, de-pending on the equipment size, with the control depending on a reflectorbehind the lamp and on the housing edge.

Theater Lighting-Control Systems

Theater-lighting circuits for both the stage and the auditorium oftenare equipped with dimming devices. The lighting should be expressiveand versatile, achieved through dimmer blending of various color circuitsand by regulating the quantity of light delivered to a particular area.When this blending or regulation is to be achieved as a part of the lightingsequence, the gradations of light should be produced smoothl}' and ac-curately.

Dimmer control of auditorium lights facilitiates eye-accommodation.Even relatively low auditorium levels may cause momentary blinding glarewhen the lights are switched on immediately after either a dark stage settingor a motion picture has been viewed.Most dimmers regulate light output by varying lamp current. Indi-

vidual preheat-starting (hot) cathode fluorescent lamps cannot be dimmedconveniently in this manner over a wide brightness range, since the arcextinguishes with a small voltage drop. However, the output of incandes-cent lamps and instant-starting cylindrical (cold) cathode lamps may becontrolled smoothly over a very wide range. The most common dimmer isthe resistance type. When not loaded beyond their rated capacity, re-sistance dimmers can handle smoothly the circuit to be controlled anddissipate the heat produced by its operation. Circular dimmers are de-signed for loads as high as 4,000 watts. When resistance dimmers have toolittle load for their rated capacity, complete blackout of the circuit is notpossible. This condition is corrected by the addition of dummy loads orby the use of other types of dimmers, particularly variable autotransformerdimmers or electronic tube-reactor dimmers.

Churches

Lighting for churches should be co-ordinated with the church service,and suited to the architectural design. (See Fig. 10-62.) Soft well-diffused illumination is recommended. High levels attract the attentionof the worshipper to the altar or pulpit at certain points in the sendees.The amount of illumination provided at the pews should be keyed to theamount of reading expected of the congregation, some of whom may have

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