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Equalizing Sight and Sound
Continued from Page 4
their trust in focusing scales and marks on the lens barrel, and seldom bother to look at the screen. The "projectionists" not only use their eves at frequent intervals, but enlist the aid of low-power binoculars or screen telescopes when their projector lenses have focal lengths longer than 5 inches.
It goes without saying, of course, that bad focus is not always the projectionist's fault. A conscientious projectionist really suffers when a "fuzzy" print comes his way. The projected picture can never be clearer than the image printed on the film: and the larger the screen, the worse an out-of-focus picture looks. Excessively high arc currents produce out-offocus effects by aggravating the rapid flutter and buckling of the film at the aperture: and the use of lenses under 4 inches E. F. makes the picture very difficult to keep in focus. as is well known in these days of VistaVision and cropped apertures for non-anamorphic projection upon wide screens.
These unavoidable causes of blur nevertheless cast no aspersions upon the projectionist's competence when conditions are the same in both projectors, as they should be.
The use of different makes, models, or "speeds"' of projection lenses in the projectors can cause sufficient difference in the appearance of the pictures projected by the two projectors to make changeovers perceptible even when two lenses have exactly the same focal length. It is extremely unwise, for example, to use an uncoated lens in one machine and a coated lens in the other. The projectionist, in such a case, may be the victim of necessity; but such a state of affairs is not good for the exhibition business. These remarks apply in equal force to CinemaScope anamorphic attachments.
Very similar to this is the use of different kinds of arc mirrors in the two lamps — or even one new and one old mirror of the same brand and specifications. Except for a brief period of testing and comparison, a dichroic I "cold" I mirror should never be
paired with a silver mirror. The light from one machine may be dimmer than that from the other, and of a perceptibly different color — slightly more yellowish, bluish, pinkish, or greenish. A change of screen-light color at the changeovers is most noticeable during the showing of blackand-white prints.
Difference in arc-lamp adjustment also cause mismatched light, but the projectionist should not rely wholly on the tape-measure and the alignment rod. necessary as these aids are. Small differences in mirror focal length, arc current, mechanism shutter transmission, and port-glass transmittance can result in a brighter light from one machine even when the geometric focus I distance from the positive crater to the center of the mirror) and the working distance I center of mirror to film aperture I are the same in both machines, and both lamps arc in perfect optical alignment.
1. Nevertheless, the first step in equalizing the light from both pro
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International Projectionist May 1964