The motion picture projectionist (Oct 1927-Sept 1928)

October, 1927 The Motion Picture Projectionist 31 Splices Splicing, whether done in the film laboratories, film exchanges or projection rooms, has such direct bearing on the welfare of the film as to call for special and constant attention. Much film is ruined by poor splicing. Splices that are wide, stiff, buckled and out of line cause the film to jump the sprockets resulting in torn perforations or breaks. Perforations in the vicinity of a splice of this kind will always be found to be strained or broken out. Stiff and buckled splices are caused by excessive scraping of the ' film, or a too liberal application of cement or both. The use of a poor quality cement results in splices pulling apart especially in the film gate or trap. This constitutes a hazard ; therefore, all weak or otherwise bad splices should be remade before projection. Figure 1 shows the well known full-hole splice which is the most widely used and if properly made gives the best allaround results. Pamphlets on splicing instructions may be had without charge on application to the Eastman Kodak Company, Rochester, N. Y. Whenever film is damaged on a projector, it is generally customary to lay the cause of the trouble to one or more of three different things ; namely, sprockets, idlers, and tension exerted on the film by the springs in the gate or film trap. While it is true that in most cases the trouble can be traced to one or more of these points, it must be admitted that the direct cause of a great amount of film damage is never definitely settled between the film Exchanges and the Projectionists, especially when the projectors in question have been gone over quite carefully and everything has been found to be in apparently good condition. In cases of this kind, it is only natural to assume that the film stock is at fault. There are, however, various projector parts, generally considered more or less unimportant which, as a rule, receive little or no attention on the part of the Projectionist. The result is that film trouble is apt to start at any one of them. The following resume covers the more important points which must be given careful attention by the Projectionists, if the maximum wearing qualities are to be obtained from the film. Tension on Springs in Gate or Trap One of the principal sources of trouble is the use of excessive tension exerted on the film by the springs in the gate or trap. A great variation will be found in tension on various projection machines being used in the trade. Moreover, there are some Projectionists who are not familiar with the amount of tension which should be used, and as far as we know, there is no set standard which is generally accepted as being correct. It is common practice to set the springs -just tight enough to hold the film stationary at the speed which is used in a given theatre. For proper screen reproduction the speed of a projector should be determined by the action of the picture. This is very seldom done, the average program being run at one set speed regardless of the Fig. 1. The Full Hole Splice Generally Recommended. action. This cannot be considered the fault of the Projectionist as he is under a certain time limit to project a given number of reels. Excessive tension as high as 34 ounces has been found to exist on certain projection machines and causes badly nicked and pulled out perforations. Heavy tension on one side can be caused by a poorly adjusted, weak or broken spring and results in an uneven pull-down strain on the film. On projectors using the gate a stop or catch is provided which holds the gate in the same position each time it is closed. Projectors using a trap door or pressure plate are not provided with a stop of any kind, thereby allowing varying amounts of tension to be applied to the film. The trap door or plate should never be let back against the film with great force as this results in exceptionally heavy tension, which must be withstood by the film until the door or plate has worked back to its proper position. The proper tension exerted by the springs should be 8 ounces for each spring or 16 ounces combined tension. Below Figure 2 is given the proper method of making a tension test. Referring to illustration B : first the tension on one side and then on the other is taken by using one half of a strip of film about 8" long. This strip is prepared by slitting a piece of film down through the center. Care should be taken to observe that the perforationson this strip of film are free of the teeth on the intermittent sprocket and are held properly in place by the tension shoe before pro G3L XL Fig. 3. A tension test is then made on both sides. 1 is the film ; 2 the pressure plate and 3 the balance at 1 6 ounces. Fig. 2A. A spring balance graduated in ounces is convenient for tension tests. Fig. 2B. Tension tests are made on each side. 1 is the film, 2 the pressure plate and 3 is the spring balance at 8 ounces. ceeding further. After fastening the end of the strip of film to the balance a straight even upward pull is made until the 8 ounce mark is reached. At this point the film will start to pull from the gate if the spring is set properly. The combined tension of both sides is then checked as shown in Figure 3, using a full width piece of film placed in the gate so that both sides of the shoe hold it firmly against the aperture plate. After making sure that the perforations on this strip of film are not engaged by the sprocket teeth proceed as before with a straight upward pull until the 16 ounce mark is reached. At this point if both springs are adjusted correctly the film can be pulled from the gate. To make this test