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PRECISION RECORDING INSTRUMENT FOR MEASURING
FILM WIDTH*
S. C. CORONITI AND H. SCOTT BALDWIN**
Summary. — The paper discusses a mechanical electronic device which continuously measures the width of film to an accuracy of 0.002 mm. The basic circuit is quartz oscillator having a L.C. circuit which is slightly detuned from the resonant frequency. The percentage detuning gives a measure of the film width. Curve shows that for a film variation of 0.250 mm the relationship between film width and measurable current is linear. An inexpensive 0-1 milliammeter can be used without sacrificing accuracy,
Precise measurement of film width is of direct interest to cinematographers, laboratory technicians, and projectionists only so far as it assists the equipment designer and the film manufacturer to provide them with materials that will give optimum performance at all times. With standard equipment and film of standard dimensions, the creative branches of the film industry can direct their energies toward production of the finest pictures, unimpeded by technical problems that were inescapable some years ago.
Motion pictures, especially 16-mm films in which minor dimensional variations are of relatively greater importance than in 35-mm films, are being used increasingly for scientific investigation and the automatic recording of data in industrial operations. In such work, problems in connection with film steadiness and dimensional characteristics, which would not arise in normal motion picture production, sometimes assume an importance that calls for dimensional measurements of the utmost accuracy.
The exact control of width during manufacture of 35-mm, 16-mm, and 8-mm film has always been a problem in the photographic industry. Obviously, before any effective measures for control can be adopted, it must be possible to measure width of the film most accurately to determine the nature and extent of variations which, in turn, serve as clues to factors causing deviations from the norm.
* Presented at the 1942 Fall Meeting at New York. ** Agfa Ansco, Binghamton, N. Y.
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