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Problems In The Use Of Ultra-Speed Negative Film
By P. H. ARNOLD
Agfa-Ansco Corporation, Binghamton, N. Y.
NEW photographic problems have arisen from the introduction of motion picture negative films having a greater increase of speed over the prevailing types than the supersensitive panchromatic films had at the time of their introduction. Some of the problems confronting motion picture cameramen and laboratory technicians can be considered in the light of solutions that have been evolved by theory and practice.
In general, Ultra-Speed panchromatic film, compared to Superpan negative film, is much faster; slightly flatter in gradation; similar in color-sensitivity, with slightly greater response to red light; and possessed of a somewhat coarser grain. Of these characteristic differences, the speed relationship has the greatest magnitude.
The Problem of Correct Exposure
A wide variety of tests made under a number of conditions of practical photography have shown that Ultra-Speed panchromatic film is correctly exposed when given two lens stops less exposure than Superpan negative film. Since the principal application of the film tends toward those conditions of photography or to cinematographic subjects that have been considered difficult to photograph or impossible to record because of insufficient illumination the problem of correct exposure can not always be solved by reference to correct exposure technic for supersensitive panchromatic negative films.
Actinometers, or exposure meters, are of little assistance under these dim light conditions since the camera position is usually remote from the subject, which, in turn, is often inaccessible for average brightness measurements. Moreover, the photographic subjects made practicable by the Ultra-Speed panchromatic film usually have too low a brightness level to activate photoelectric exposure meters in common use. Fortunately the sensitivity characteristics of the new film are sufficient to produce successful pictures under typical indoor illumination, with normal shutter angles and at camera speeds of 24 frames a second, using lenses having relative apertures of f/2.3 and, in some cases, f/ 3.5.
The speed of the film is not appreciably affected by age. No allowances need be made in exposing old film since the Ultra-Speed film has proved to
*Abridged from The Journal of the Society of Motion Picture Engineers,
September, 1938, Vol. XXXI, No. 3.
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