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FIG. 8. Pleating caused by a break in the soundhead and resultant folding of the film.
Misunderstanding still exists concerning the general performance of safety film. Many projectionists are under the impression that the present high acetyl type safety film is the same material which they may have encountered in the years past. This is not so. Present day safety stock now replacing all nitrate film has properties which are fully suited to the requirements of commercial use. The projected screen image obtained from the new safety film is equivalent to that obtained from the former nitrate base materials. In many respects, the new safety material is superior to the nitrate film formerly supplied. Splicing should not be any more difficult with the new film than with nitrate base materials if the proper procedures are followed. A splicing unit of some kind, however, is definitely recommended. Hand splicing will not give dependable results today.
Increased Screen Brightness
In recent years much interest has been shown in the problem of obtaining higher screen illumination, particularly for use in drive-in theaters and for indoor theaters having very large screens. Increased illumination has been made possible by developments in high speed optical systems and new types of carbon arcs. With the increase in the screen illumination, there has been a corresponding increase in the temperature of the film at the aperture. The film characteristics place a limit on the maximum light available for screen illumination, since as it is heated to higher temperatures a point is reached beyond which satisfactory projection becomes difficult. Still further increase in temperature may ruin the film beyond hope of repair.
One of the first effects noted in the film as projection intensity is increased is an embossing of the frames and of the image within each frame. When examined by reflected light, at an angle nearly coincident with the plane of the film, each frame can be seen to stand out like a small cushion and frequently the image itself appears as though it
were carved into a small plaque. Most film, after having been projected, shows some embossing and the extent of this embossing increases with the light source intensity. This embossing, how
ever, even when severe, does not impair the screen image quality, although when embossed film is spliced to unembossed film it may be necessary to refocus slightly at the splice.
As the light source intensity is increased still further, the film may, in many cases, show a discoloration of the image. This discoloration is not noticeable when the picture is projected upon the screen but when the film itself is examined against a piece of white paper, the frame areas show a distinct sepia tint. No real danger to the print exists, however, as a consequence of this effect, since it is still capable of giving a top quality screen image.
However, if the intensity is increased still further, an in-and-out-of-focus ef
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FIG. 9. These prints were ruined by blistering caused by excessive aperture temperature.
INTERNATIONAL PROJECTIONIST • April 1952
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