International projectionist (Jan 1963-June 1965)

Fig. -i — In exploring the possible causes of weave-producing variations in film shrinkage, the effect of the flange design of shipping reels is mentioned in the accompanying article. Is the film more quickly affected by humidity and heat where exposed by the large holes than where covered by the solid portions of the flanges? Other suggested causes of shrinkage variations are oil mottle on film, deposits of edge-wax, and uneven or careless rewinding of the film for shipment or storage. feasible r\ni though all presently used theatre projectors allow a longer length of film to exist between the sprocket and the aperture. This suggestion is nothing new to the manufacturers of cameras, optical printers, and background projector heads. They wisely position their claw pulldowns and registration pin vejrj close to the aperture, thus practically eliminating the annoying effects of an) shrinkage variations which ma) be present in the film-. Possible Causes of Variation It is possible that variations in the tightness of the film in a roll may induce irregularities in shrinkage by \ irtue of uneven mechanical strain. Stresses of this nature ma\ be verj significant during the natural aging-shrinking period in the life of the film. For this and other reasons the projectionist should make certain that his projector takeups and bench rewinders are properly aligned and wind up the film smoothly under reasonably uniform tension. Film which has been roughly or irregularly rewound on hand rewinders las during inspection and print repair I should never be stored or shipped out until after it has been smoothly rewound on a low-speed motorized machine having accurately aligned elements. The exchanges' suggestion that the reels of film be returned without rewinding after their last showing is a very good one. as projectors in good working order wind up the film very uniformly. Nevertheless, many projectionists refuse to use shipping reels in the projectors, admittedly a dangerous practice when the shipping reels are badly bent and battered out of shape. It is clearly the responsibility of the film exchanges to provide good reels. It is also possible that the flanges of metal shipping reels permit a differential "conditioning" of film by exposing the edge of the roll to free circulation of air through the large holes in the flanges, and covering the edge of the roll under the solid sections. The writer personally believes that this could be a significant factor only when the reels of film are removed from the shipping cases in an unusually hot and humid ("quick-acting") International Projectionist August, 1963 atmosphere. In any case, film should be wound on a core as a bare roll and placed in a metal can for long-term storage under the conditions recommended in the booklet "Storage and Preservation of Motion Picture Film" (Eastman Kodak Co., Rochester, N. Y., 50c). Still another possibility is that variations in the distribution of projector oil, grease, lubricating wax, etc. adhering to the film is the cause of some shrinkage-variation in used release prints. Moisture presumably passes into the film more slowly through oil than when unobstructed. And if the film is subsequently cleaned with carbon tetrachloride. Freon compound, or methyl chloroform, possible extra loss of film solvents with the removed oil and dirt might conceivably alter the pattern of shrinkage variations. This is a matter worthy of study by film technologists because we know so little about the effects of oil, wax. and cleaning fluids on film shrinkage. Booth "Treatment" of Film Tabu Except for the cleaning of short rolls of trailers and announcement titles in the projection room with a pad of soft cloth moistened with film-cleaning fluid, no attempt should be made by the projectionist to undertake an exfensive and tricky cleaning job which is the responsibility of the exchange supplying the print. Careless cleaning, with failure to renew the soiled pad frequently, may scratch and mottle the film. The Kodak booklet mentioned previously gives directions for cleaning film manually. Never — and we mean never! "humidify" or '"steam-treat" motion-picture film! With the best of intentions a few misguided projectionists have been known to pass film through a steaming arrangement while rewinding it and to store the reels in bins having wet blotters or open pans of water. The idea, of course, is to "restore the moisture" expelled from the film during projection. These are not approved methods for "restoring moisture" even if that expedient were deemed desirable. Treating film with steam will ruin it. Storing it in humidifiers or over water will hasten shrinkage, possibly shrink it irregularly if the film is put into a moist atmosphere while still warm from the projectors, spot the emulsion, and lay the film open to fungus attack. Other Causes of Weave Examination of picture quality in theatre after theatre indicates that sidesway originating in flat-gate projectors, especialh in CinemaScope anamorphic projection, is a more serious matter than the very small amount of vertical unsteadiness which in most cases is visible only from a vantage point relatively close to the large theatre screen. Such unsteadiness is only rarely troublesome, but it would be best not to have any unsteadiness at all. Naturally, there is nothing the projectionist can do to correct matters when a jumping picture is printed on the film, as is sometimes the case with technically unpretentious pictures of foreign origin and with reissues printed from old negatives. Although there is some evidence that shrinkage variations in well-worn prints is rather common, it would be a big mistake to assume that all random small-range vertical weavings of projected pictures are due to this cause alone. If the intermittent movement of the projector is in good condition, and the teeth of the sprocket unworn, similar effects can be produced by uneven gate tension, the wrong amount of gate tension, a loose intermittentsprocket shoe, the bad practice of making excessively large upper and lower film loops, torn or badly abraded perforations, and an unsteady pedestal or support for the projector. iP