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1952 Theatre Catalog, 10th Edition, Page 294 (258)

1952 Theatre Catalog, 10th Edition
1952 Theatre Catalog
1952 Theatre Catalog, 10th Edition, Page 294
Page 294

1952 Theatre Catalog, 10th Edition, Page 294

FIG. 7. 'l'vpes oi perforations used on 35mm. motion picture films.

foration with the good wearing properties of the Standard Positive type perforation. It is used for certain color release print films because it allows sharply registered images to be obtained during the printing operation. The vertical and maximum horizontal dimensions of this perforation are the same as those for the Standard Negative perforation of Figure 7A. The horizontal dimension of the Standard Positive perforation, shown in Figure 7B, is the same as that for the other two but its vertical dimension is somewhat greater.

While every step is taken during manufacture to insure that motion picture film will fulfill the requirements of general commercial use, consideration should be given to the fact that it has

physical limitations.


Good projection, which adds patronage and increased revenue to the theatre, is entirely dependent on the skill of the projectionist and the condition of the film and the projector. Satisfactory screen reproduction is not possible with a bad print regardless of how efficient the projectionist might be. Likewise, good results with a perfect print cannot be expected from faulty projection equipment. Through constant use, projector parts become worn and out of adjustment. The replacement of worn or dame aged parts when needed represents a wise investment because any expenditure in this direction will improve projection and materially reduce unnecessary film damage.

While the maintenance of the projection equipment is the responsibility of

the theatre, the projectionist can do many things which will aid in eliminating print damage. There are, for example, various projector parts which may sometimes seem unimportant but which demand frequent attention on the part of the projectionist. Film damage may occur at any one of them and may often be avoided if adjustments are made at the proper time and if damaged or worn parts are discovered and replaced promptly.

The following resume covers the more important points which must be given careful attention by the projectionist if the maximum wearing qualities are to be obtained from the film.

Magazine Valve Rollers

It should be remembered that severe abrasion is often the only reason for discarding a print. It is probable that more film is scratched in the magazine valve rollers than at any other part of the projector. This is especially true for those rollers in the upper assembly, Figure 8, the first point of contact with the film after it leaves the feed roll. At this point, dirt, oily matter and film chips may accumulate so as to prevent free turning of the rollers or they may become so clogged that one or more of the rollers may not turn at all. The roller tracking may also develop flat spots and wear down to the point where the center of a non-turning roller is in direct contact with the film. Under these conditions, the relatively soft emulsion of a new print is very susceptible to abrasion and the scraping is frequently so deep that the emulsion is completely plowed off, as shown in Figure 9. Support-side scratches show up as dark lines on the screen and might be equally disturbing, particularly when they become filled with oil and dirt. With duplitized film (certain types of color prints), there are two emulsions which are affected. Most projectionists are familiar with the objectionable red and green

FIG. 9. Abrusions caused by defective or clogged magazine valve rollers.

FIG. 8. Magazine valve rollers.

ttrainf or deeper scratching on some of the duplitized films.

Straight scratches and those that weave slightly in a repeating pattern due to uneven reel flanges moving the film from side to side, can be caused by the valve rollers, although the perfectly straight abrasions are more often associated with some guided position.

Padding of Trap Doors

Occasionally release prints are encountered which give a slight flutter in the gate or trap. This gives a slight inand-out-of-focus effect on the screen. In an effort to control this Hutter, some projectionists fasten strips of pressboard, velvet, or layers of tape between the tension pads, both above and below the aperture, thereby discouraging any forward motion of the film. A standard trap door with layers of tape in position is shown in Figure 10. This practice cannot be recommended because it can cause serious support-side abrasion, particularly in the case of films having a higher positive curl than usual. Increased curl is a common condition with newer prints during dry winter months.

Abrasion Due to Positive Curl

In the case of prints having higher positive curl there is always a possibility of support side abrasion at some other point which is normally not contacted by flat film. Attention has already been drawn to the importance of making sure that the valve rollers turn freely. Another place at which contact may occur is at the intermittent guide holder. On Sonic projectors the center clearance

1952 Theatre Catalog, 10th Edition, Page 294