We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
286 RICHARDSON'S BLUEBOOK OF PROJECTION
align it exactly with the projector head. When this has been accomoplished the lamphouse is firmly locked in place on the sloping platform. The slope of the platform can be altered by the hand wheel seen the left, top, of the pedestal, and the adjustment of this wheel can also be firmly locked. When the tilt of the lamphouse platform is changed, by means' of the hand wheel, the angle of the protruding member to which the projector mechanism is mounted also changes, keeping lamphouse and mechanism in perfect alignment. The protrusion at the left of the pedestal is the casing of the switch which controls the current to the light source. The pedestal is hollow, and in modern installations conceals and shields electrical wiring, which is brought up through the floor. This wiring can be reached by pulling out the removable panel, visible in the photograph some little distance below the trade mark.
(10) To understand the principle of action of the projector mechanism it is necessary to be very clear about the mechanical requirements of motion picture projection. A reel of theatre-type film contains 12 separate photographs for each 9 inches of its length. These photograph vary in shading from transparent to completely black. Each of them must be interposed briefly between a source of brilliant light and the screen on which the audience views the picture. When this is done the light streams through the photograph and with the help of proper lenses is focussed upon the screen, presenting an enlarged duplicate of that photograph before the audience. Twenty-four of these photographs are projected before the audience each second to produce the illusion of motion.
(11) As much as 2,000 feet of film, wound on a metal reel, is placed in the upper magazine of the mechanism. The lower edge of that magazine can be seen in Fig. 125'. The reel in the upper magazine is free to spin on an axle provided for it, thus permitting the film to be unwound. A few feet of it are unwound, and "threaded'' into the mechanism, as will be explained later. Fig. 125 shows film properly threaded. Let us trace the path of the film