Transactions of the Society of Motion Picture Engineers (1916)

parison with brick or concrete, light in weight (an important consideration in some circumstances), quite thoroughly soundproof by reason of its interior air space, sufficiently rigid for all practical purposes; also it neither absorbs nor retains the heat to any appreciable degree. Hollow tile is, therefore, the best possible medium for projection room wall and ceiling construction. Four-inch hollow tile may be used for the ceiling, but six-inch is best for the walls. Next in order of excellence is concrete. The objections to this material, as compared to hollow tile are threefold, viz.: excessive weight, absorbs and retains heat, and, unless of considerable thickness, acts to some extent as a sounding board to distribute sound inside the room out into the auditorium. Following concrete comes brick. Its objections are weight, cost, heat-absorbing qualities and difficulty of ceiling construction, where same is necessary. For permanent installations what is known as the asbestos room should not be considered at all, except its present construction be radically changed. As at present made its ceiling is not high enough; also, its walls and ceiling act as veritable sounding boards for the distribution of sound, though it forms an acceptable fireproof room for strictly temporary installation. With double walls and ceiling, with an air space between, and an eight or ten-foot ceiling height, it would serve very well for permanent use. Dimensions: It is not to be reasonably expected that the projectionist will do his best work if placed in crowded, cramped quarters. Space inside a theatre is valuable, especially if it can be utilized for seating, hence exhibitors begrudge every inch surrendered, and usually try to reduce the projection room to its least possible dimensions, which is extremely poor policy, when carried to the point where projection is made to suffer. So far as the writer knows, up to date every legal standard set up for size calls for a too small depth, front to rear. The shortest of modern professional projectors measure four feet three inches front to back when setting level; considerably more when at an angle. The setting of projection machines up against the front wall is poor practice. There should be at least i8 inches between lens and wall when machine sets level, and not less than three feet in the clear behind the projectors. Taking everything into consideration, nine feet may fairly be set up as a standard front to rear depth for projection rooms, with the notation that ten feet is better. The width of the room should be a minimum of six feet for one machine, with three feet of added width for each additional projector, spot lamp or stereopticon. The minimum distance from the floor to the ceiling should be eight feet, with the recommendation that added ceiling height be provided where possible. A high ceiling is very desirable, both from the viewpoint of health and comfort and in case of fire, since it provides a reservoir for the heated air above the heads of the men, and for gases and fumes, should a fire occur. Ventilation: This is indeed a most important item. Let it be first understood that pulling the fetid atmosphere in from the top of a hot auditorium through the projection room ports does NOT constitute ventilation. The projectionist is human, and it is nothing less than a 32