Ch. XII]
DARKENING THE PROJECTION ROOM
443
The indirect or concealed light sources which have been recently
developed answer all the requirements for suitably lighting a mov¬
ing picture theater or, indeed, any other place where a soft light is
required and the light should not shine directly in the eyes of the
spectators (fig. 237 A, B, C).
It is also an advantage to have the screen in a kind of alcove 1 to
2 meters (3-6 ft.) deep and the walls on the sides, the floor and the
ceiling dark brown or dark red or olive to absorb any light reflected
upon them (606a).
For exhibitions, it also adds brilliancy to the picture to have a
black border around the screen. It gives also the effect of a framed
picture.
With such an arrangement of the lights in a suitably tinted room,
no light will reach the screen directly to destroy the contrast and
render the image vague. There can be sufficient diffused light in
the room to enable one on entering to sec the aisles and seats, and
go about without stumbling. In a short time twilight vision will
be established and it will then be possible to read or to take notes.
§ 607. Red lights near all exits. Fire escapes.—In public
halls, and especially in moving picture theaters, it is an advantage,
and often a requirement in city regulations, to have red lights near
every exit so that the audience can see exactly where it is possible
to get out of the hall.
The manager of every public hall should look to it every day that
the fire escapes are in working order and before every exhibition
that the doors or gates to the fire escapes are unlocked and easily
opened.
§ 608. Relative darkness of the room for different kinds of
projection.—The amount of diffuse light permissible in the pro-
§ 606a. While it is a great help to have a screen in a dark alcove, still the
general light of the room, although none extends directly upon the screen,
tends, if too great, to make the image less brilliant and definite. Every one
who has studied astronomy at all with a telescope knows full well how the
definiteness of the image of a nebula or dim star cluster diminishes when the
moon rises and floods the heavens with its diffuse light. One can also see the
effect of too much diffused light by observing a lighted clock face on a dark
night, and the same face with the same light shining from it on a moonlight
night or early in the evening twilight before complete darkness.