International projectionist (Jan 1959-Dec 1960)

celerates after passing the pulldown peak of maximum velocity. The gradualness of the acceleration and deceleration of the sprocket makes the 35mm geneva intermittent movement both quiet and kind to the film at all pulldown ratios from the unmodified 3-to-l to the "accelerated" 5-to-l ratio (Simplex X-L Hi-Speed). The Drunk-Cam Movement The drunk-cam sprocket movements, depending as they do upon a specially grooved cam and a pinwheel or roller-wheel device for the pulldown action, can be made to work at almost any desired pulldown ratio and with the desired acceleration-deceleration characteristics. Although somewhat more difficult to manufacture than geneva movements of comparable quality, they are nevertheless ideal for 16mm machines because of their quietness and gentle handling of the film. It seems strange indeed that the drunk-cam type of movement has not come into as wide use in America as in Europe for narrow-gauge projectors. The high-speed claw movements used in most American 16-mm machines are murderous to the film and so noisy that, if installed and used for a long time in theatre projection rooms, chronic deafness would surely become the chief occupational hazard of the projectionist's profession! A wider availability of the popular high-grade European projectors on this side of the Atlantic would be most welcome. Feed FIG. 1. The film-contacting components of the film path of a standard American-type theatre projector. The complete film path of a modern theatre projector may seem complicated to the uninitiated, but it is designed for ease of threading and satisfactory accomplishment of three special functions: (1) intermittent movement of the film in the mechanism gate, (2) super-smooth continuous film travel past the soundhead scanning beam, and (3) the trouble-free winding of the film on the takeup reel which may hold 2000, or even more, feet of 35-mm film. Figure 1 shows the film path of the usual American type of theatre projector, all parts omitted from the drawing except those which actually touch the film. (The film course of the usual European type of theatre projector is slightly different due to a different placement of the sprockets, rollers, and sound reproducer, but the essential parts — feed sprocket, gate, intermittent sprocket, and sound and takeup sprockets — are arranged in the same order.) Lateral Guide Rollers Let's concentrate upon that section of the film path which is particularly vital to projection quality, the gate of the mechanism. We find (1) flanged lateral guide rollers at the top of the gate, (2) polished steel runners upon which the perforation margins of the film rest, (3) a gate door with tension pads to hold the film flat in the gate, (4) the picture-window, or aperture, (5) the intermittent sprocket, and (6) the intermittent-sprocket shoe (usually attached to an apron on the gate door) . All these parts are shown in Fig. 2. 1. The lateral guide rollers align and steady the moving film sidewise. The lateral positioning of the outer "fixed flange"— the one nearest the projectionist as he stands at the operating side of the machine — determines the alignment of the film. This flange should never be moved more than about 1/32 inch on either side of its median position, however, or the film may be twisted slantwise in the gate just enough to enage the teeth on only one side of the intermittent sprocket. The inner movable flange — the one farthest from the projectionist — is spring-loaded to press gently upon the edge of the film and bring the film up snugly against the fixed flange. The edge of the film nearest the projectionist as he stands in operating position is accordingly the guided edge. The FIG. 2 Component parts of the film gate: A, the film runners; B, the aperture plate; C, the flanged lateral guide rollers; D, the intermittent sprocket; E, the intermittentsprocket shoe, and F, the gate-tension pads. soundtrack lies just inside the perforations in the guided-edge margin, so this edge is also guided in the soundhead. The physical condition of the flanged guide roller is just as important a matter as its lateral positioning. After adjusting the unit laterally and tightening the set screws in the collar so that the picture is properly centered on the screen, make certain that the flanges turn easily. As a matter of fact, the film itself should cause them to revolve slowly. Very light spring pressure, cleanliness, and one small drop of oil will insure their turning. Failure of the flanges to revolve will result in scoring by the film. A scored flange may shear the edges of the film, tear weak splices apart, and cause severe sidesway of the projected picture. Sidesway and picture-weaving are also caused by spring tension great enough to "pinch" and buckle the film as it enters the gate. Test the degree of pressure with your finger and observe the behavior of the film as it passes from the upper loop into the gate, and remember that the CinemaScope anamorphic lens doubles the amount of sidesway. Why "Studio Guide Rails"? Several modern projectors are fitted with "studio guide rails" in the gate, for what purpose we know not. Release prints vary in width because of shrinkage: an edge-to-edge distance INTERNATIONAL PROJECTIONIST • SEPTEMBER 1959