International projectionist (Jan 1943-Dec 1944)

A Complete Study on the Prevention of Film Damage By HENRY B. SELLWOOD '"Film damage" is by no means a new phrase to any of us. The subject has been talked about and written about ever since the first pictures were shown on screens. In most studies of the subject usually only one phase of film, damage is covered, leaving the many others to subsequent articles, with the result that no complete picture of the subject has been given in a single presentation, such as is featured herein. No one phase of film damage is less serious than any other — all are equally important. They all contribute to the showing of a poor picture and shorten the life of the film. As every projectionist should be interested in putting on the best possible show it follows, therefore, that all should know how to guard against every phase of film damage, with each being covered fully in the accompanying article. ALL film damage comes under two classifications: scratching and mutilation. Scratching of film may be due either to dirt or a sharp point or jagged surface coming in contact with the film. Dust can be found in every projection room and there usually is present oil vapor and air moisture. Either or both of the latter naturally are deposited on the film, thus any oust coming in contact with the film remains on it. Dust always contains a certain amount of gritty or abrasive material, so there is a nice abrasive coating on the film ready to scratch it when two surfaces of the film slide over each other or when the film slides through the projector on its way from the upper to the lower magazine. Jagged surfaces or sharp points need little if any clarification. If there are any sharp projections in the film path that the film may come in contact with, the film will be scratched. Mutilation covers everything else that may happen to a film in the way of impeding its usefulness. Torn sprocket holes is the first example that will undoubtedly come to mind, it being all too common. Other examples are torn edge?, splices opening resulting in film pileup and damage, cracked film from too sharp bending, and warping and buckling of film. Torn sprocket holes usually are thought to be due only to hooked sprocket teeth or too great takeup tension. It is possible to weaken the sprocket holes by improper positioning of the film over the sprockets and then closing the pad roller or the gate. Here we have the possibility of the film being forced against the sprocket teeth and the edge of the sprocket holes being cracked. Then the next time the film is used there is the possibility of the sprocket holes being torn. If a sprocket tooth is allowed to become hooked the film will tend to become locked to it and follow it around the sprocket until the next sprocket or guide roller tears it loose. Something has to give and it will be the film. All sprockets should be examined carefully and frequently and at the first evidence of the teeth becoming undercut the sprocket should be reversed, if possible, or a new one substituted. In case a new sprocket cannot be obtained try stoning the teeth, using a very fine carborundum block or its equivalent. Extreme care should be taken in this operation as the tooth contour has been verv carefully determined for proper operation, and any appreciable change in the angles will affect the operation of the machine. By means of a suitable fixture it is possible to prolong the life of the sprockets considerably. Preventing Torn Edges Torn edges may be caused by bent reels or projections on the sides of the gates or pad rollers against which the film may rub. All reels should be inspected frequently and kept perfectly straight. In a similar manner examine the film path for any possibility of the film rubbing against any spot that will damage the edges. An accumulation of dirt or emulsion tends to cause trouble and should not be allowed to occur. Cleanliness is extremely important. It cannot be stressed too much. Those of us who have been unfortunate enough to have a splice open up know how much damage can be done to a film. It will pile up in the most peculiar manner and take the most unusual configurators. As a result there is the possibility of torn sprocket holes, torn edges and cracked film. Film which has piled up should be examined carefully for all of the above possibilities. Sometimes cracks are not detected any too readily and require special watching. Over a period of years film cement has been much improved and the technique of splicing film developed so that open splices were very rare up to the time that the war conditions made necessary changes in the manufacture of film. Reports have been circulated that wartime film is difficult to splice. In this regard the recommendations of the film manufacturers should be followed. However, it may be said here that if the proper amount of care is exercised in making a splice, there is no reason to believe that splices will ©pen. This question of open splices has been brought up to emphasize the necessity for care in splicing and for special consideration of this essential part of operation for the duration. Film Dries Out With Age As film ages it will dry out unless definite precautions are taken to give it preventive treatment. Such treatment is being given those films that are being preserved for posterity in the various film libraries, and also in the case of those films which are preserving valuable records. As far as we know, such treatment is not used in the handling of regular theatre films. Therefore, as a film passes from theatre to theatre it becomes drier and drier. Thus it becomes more subject to cracking and in the drying process it has a tendency to warp and buckle. This process is accelerated by a dry high temperature. Therefore the temperature at the picture aperture determines how rapidly the film will dry out and how serious the warping and buckling will be. Manufacturers of projectors are very much aware of this action and the newer projectors give evidence of the consideration that has been given to this phase of design. How far the manufacturers will be able to go in decreasing the temperature at the aperture remains to be seen. A warped or buckled film can cause a lot of trouble in a projector. For example, as it goes past the sound scanning point it must be in a certain definite relation to the scanning beam longitudinally and laterally. If it is closer to or farther away from the sound optic than it should be. sound quality will deteriorate. If it is displaced inwardly or outwardly, sprocket hole or frame line noise 16 INTERNATIONAL PROJECTIONIST