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CHAPTER VIII. THE PROJECTOR
Nothing is more important to an understanding of the methods and practices of good projection than a knowledge of the projector. Projectionists often shift from theatre to theatre and encounter different types of projectors which they are expected to operate efficiently. It is easy to secure instruction books from the various manufacturers by simply writing for them. It is considered sufficient to discuss here only those fundamentals which apply equally to all makes.
The Supporting Base
All projectors require a supporting base of sufficient strength and rigidity to support the lamphouse, mechanism, sound head, etc., and to hold them without vibration. Its contact with the floor must have sufficient area to insure this condition, assuming the floor itself to be without movement or vibration. (1) In considering the projector support it must be remembered that any vibration of the projector backward and forward upon its base will be magnified many times upon the screen, the magnification increasing as the distance of the lens to the screen increases.
(2) Because absolute rigidity is required, the floor itself must be without vibration and the projector supporting stand must contact it securely by means of anchor bolts.
(3) When building a new floor, the kind and model of projector should be decided upon in advance, a template made and the anchor bolts suspended therein, with heads not less than four inches below the floor surface. The concrete is then carefully and solidly packed around
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