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Sept., 1938J
NEW MOTION PICTURE APPARATUS
311
Other Problems of Exposure. — The speed advantage of two diaphragm stops, of Ultra-Speed panchromatic over Superpan negative film, is fairly constant under various daylight and artificial lighting conditions,2 indicating close similarity in the color-sensitivity characteristics of the two films. Wedge spectrograms, however, show that the Ultra-Speed film has a slightly greater range of sensitivity to red light than the previous film (Fig. 4) and photographs of the color chart (Fig. 5) show that Ultra-Speed panchromatic film has about 20 per cent greater response to red-colored objects than the old Superpan negative film. The photographic problem introduced by these color-sensitivity dissimilarities is not great and in most cases can be neglected with confidence. No special character make-up has been found necessary with the Ultra-Speed film even under 100 per cent tungsten illumination.
Problems of Printing and Development. — In timing negatives made on UltraSpeed and Superpan negative film, no allowances need be made for differences in the gray-base color, since they both have the same type of neutral gray antihalation layer (Fig. 6) on the base underneath the emulsion. When combined for printing with other negatives having lavender, pink, or orange-tinted gray bases of similar optical density, the Ultra-Speed panchromatic film may appear to be only three times instead of four times as fast, due to selective absorption of the printing light2 by the tinted gray bases. From three to five printer points may be required to compensate for the filter
Superpan
TRAY DEVELOPED IN AGFA 17
16 2O 24 28 MINUTES
FIG. 7. Gamma vs. developing time relationship of Ultra-Speed panchromatic Supreme, and Superpan negative films.
effect of tinted gray bases that depart markedly from a neutral gray.
When developed for a gamma of 0.65 or lower, Ultra-Speed panchromatic film has a flatter gradation than Superpan negative film given the same treatment (Fig. 7). When developed for a gamma of 0.7 or higher, the Ultra-Speed film becomes progressively steeper in gradation than Superpan negative film given the same treatment. Considering the contrast relationship of the two films in the range of negative gamma normally employed in professional motion picture work, together with the photographic characteristics of the subjects that usually will be photographed on Ultra-Speed panchromatic film, best screen results appear to follow the practice of developing Ultra-Speed panchromatic film about 20 per cent longer than Superpan negative film.
In professional motion picture work, Ultra-Speed panchromatic film will, of necessity, be developed under normal negative processing conditions in prevailing types of developer, with the correction in time of development noted above. Tests with a number of developer solutions of interest to the photographer who uses motion picture negative film in miniature cameras for still photography have shown that Ultra-Speed panchromatic film behaves at least as well as Superpan negative in these solutions. For example, the rate of exhaustion of developer