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Reducing and Intensifying Solutions for Motion Picture Film

1931; Volume: 17; Issue: 6 Linguagem: Inglês

10.5594/j07492

0097-5834

J. I. Crabtree, L. E. Muehler,

Color Science and Applications

The properties of a large number of known intensifying and reducing solutions have been studied in detail to determine formulas suitable for use with motion picture film. — For intensification, the chromium, Monckhoven (mercury), and silver intensifiers were the most satisfactory. The Monckhoven intensifier is useful for extreme intensification where permanence is not essential and the chromium intensifier is suitable for negatives where a medium increase in contrast is desirable. The degree of intensification with the chromium method may be controlled within limits by a variation of the time of redevelopment. For negatives and projection prints, intensification with silver has been found to give strictly neutral images and the process permits of easy control of the degree of intensification. So far as is known, both the chromium and silver intensified images are stable. — For subtractive reduction, such as in the case of overexposures or fogged images, the use of either (1) a two-bath formula comprising separate solutions of potassium ferricyanide and sodium thiosulfate, or (2) a modification of the Belitzski reducer is suitable. Where proportional reduction is required, a solution containing ferric ammonium sulfate with sulfuric acid is recommended. — It has been found that the above methods of intensification and reduction are applicable to sound film with the possible exception of subtractive reduction which, by virtue of the lowering of resolving power, causes a loss of high frequencies.