The motion picture projectionist (Nov 1931-Jan 1933)

18 Motion Picture Projectionist April, 1932 Use and Care of Motion Picture Film By H. L. Kooser and Charles Roach The subject of the Use and Care of Motion Picture Film is one of paramount importance to every projectionist. In the treatise which follows, the authors note some of the common troubles experienced with film and offer suggestions for correction and prevention of them. No claim is advanced that the information which is supplied is revolutionary or startling in its character, but the article contains much that cannot fail to be of assistance to the discriminating reader. Mr. Kooser is a member of the staff of the Visual Instruction Service of the Iowa State College, Ames, Iowa, and the material is published through the courtesy of that institution. Mr. Roach was formerly Director of Visual Education, Los Angeles Public Schools. — The Editor. THERE are today two general types of motion picture films in use, the nitrate of cellulose or inflammable stock and the acetate of cellulose or non-inflammable stock, more familiarly known, perhaps, as "safety" film. "Safety" film is so indicated by the word "safety" which is printed at intervals along the outer margin of the film. The inflammable stock is used almost entirely in theatres while the "safety" stock is coming to be used more and more for educational purposes. Theatres are better able to cope with the fire hazard, and inasmuch as "safety" film is much more subject to deterioration than the inflammable stock, they do not use "safety" material extensively. The National Board of Fire Underwriters specify that all projectors must be enclosed in standard fireproof booths when using inflammable stock. Certain portable projectors are authorized for use by non-professional operators and with slow-burning or non-inflammable stock, standard width, without booths. Local ordinances and electrical codes should be consulted at all times. Standard width motion picture film is 1% inches in width with 5.4 perforations per inch of length. All film used in commercial work is standard width. The average reel of standard width motion picture film contains about L,000 feet upon which are printed 16 separate and distinct pictures per foot. Each reel is a photographic reproduction of a series of snapshots printed from a master film or negative. Films are very fragile, easily injured and a single wrong adjustment of a projector will do irreparable damage to them. The greatest sources of trouble arise from the sprocket hole perforations and poorly made splices — sometimes called patches. During projection the film moves in front of the light at the average rate of 90 feet per minute with 16 distinct stops and starts per foot. Onesixth of the time the film is in motion and during the remainder of the time the film is motionless at the aperture. Film Deterioration At normal speed each successive picture moves into position before the aperture in approximately 1/100 of a second. It can be readily understood that there is considerable strain on the film, particularly at the sprocket hole perforations along both edges of the film. The following contribute to rapid film deterioration and subsequent projection difficulties: Dirt accumulations, worn sprocket teeth, too strong tension, poorly adjusted idlers, misalignments of working parts, surplus of oil and grit, accumulations of loose emulsion and wax, and careless rewinding, packing, shipping and storing. Fig. 1. Proper and Improper Film Repairs Film usually comes from the exchange properly wound and apparently ready for the projector. However, it is never advisable to project film without first inspecting it while rewinding from one reel to another. Even though the exchange may employ inspectors who are capable, there are times when in the rush to make shipments, the inspection is carelessly done. Loose patches, misframes, broken sprocket holes and small tears may have escaped attention. Every user of film should be provided with a bench film rewind supplied with a brake. The bench rewind, as the name indicates, should be fastened to a table, shelf or bench. A hole about 4x4 inches should be cut in the bench and fitted with a piece of ground glass. Beneath the ground glass may be placed a 5 or 10-watt electric lamp. A film mender should be permanently fastened adjacent to the ground glass on the bench or table. A bottle of the best grade of film cement (not glue or library paste), a safety razor blade or film scraper, and a small pair of scissors complete the necessary equipment. For inspection, the reels should be placed on the rewind attached to a table so that the film, while being rewound, travels from left to right, with the emulsion or dull side up. The film should be held between the left forefinger and thumb with just enough pressure to keep good contact with both sides of film. Rewinding and Inspection If rewound very slowly it is possible to detect every broken sprocket hole, tear, defective patch or misframe. Especial care must be exercised not to overspeed the rewinding process, lest the rough sides of an imperfect, bent or distorted reel may injure the film. It is impossible to detect imperfections when the film is traveling rapidly. If the film is guided into the reel properly the edges of the successive turns of the film will build a perfectly flat disc-like surface. A thousandfoot reel should never be rewound in less than five minutes — a longer time is recommended. As much damage may be done during one careless rewinding operation as would be done during many trips through a projector. The temptation to hurry has ruined thousands of feet of film. During the rewinding and inspecting operations it is always advisable to have a brake attached on the part of the rewind holding the film being rewound, so that a slight tension may be kept on the film. This is especially necessary for any reel that contains a thousand feet or more. If loosely