British Kinematography (1950)

March, 1950 coote : colour kinematography 85 Anscocolor Processing The authors commence with the plain but all-important statement that : " The continuous processing of Anscocolor film requires control of speed, gradation, fog, maximum density, and other variables common to the processing of black-and-white film, but with the complicating factor that the variables must be kept constant in each of three superimposed emulsion layers." They go on to say that three general control methods, photographic, analytical and />H, are recommended for the various testing operations. Both the first developer and the colour developer are replenished at a high rate, the first in order to avoid accumulation of bromide, and the colour developer because the replenisher is used at the maximum practical concentration. Bromide is added to the colour developer replenisher because it accumulates too slowly as the result of reduction of silver. Short-stop and hardener baths are both replenished at a high rate to prevent their contamination by carry-over of preceding solutions. The bleach is not replenished, but is regenerated when necessary by means of liquid bromine. Two bleach baths are required, one remaining in use while the other is being regenerated. The fixer is used until it is sufficiently exhausted and is then dumped for silver recovery by the sulphide method — electrolytic methods being unsatisfactory for neutral or alkaline fixing baths. Control of Anscocolor It is interesting to note that Ansco consider it necessary to construct a special control test machine in order to obtain reproducibility better than the tolerance allowed for the solution or material being tested. In other words, it is necessary to be able to process strips so that the results will not deviate by more than one-eighth stop in speed or one-sixteenth stop in colour balance when identical solutions are used for the reference and the sample. In discussing the permissible fluctuations during continuous processing, Bates and Runyon point out that the variables which cannot be absolutely controlled include differences in emulsion batches, printer exposures, chemicals, solution mixes, developing times and temperatures, circulation rates, drying conditions and even final densitometry. In practice, although the deviation due to any single one of these influences may not be serious, from time to time the additive deviation will amount to as much as plus or minus one-quarter stop in speed as well as one-eighth stop shift in colour balance. Leaving aside the preliminary testing of chemicals, raw materials and processing solution mixes, there are more than twenty regular tests required to be made at various intervals during processing. These tests include hourly checks on temperature and pH of both first and colour developer, as well as analyses of both for bromide every 4 hours, and for all ingredients every 2 days. The densitometry of any colour film involves the use of quite special measuring instruments, and for their work Ansco have undoubtedly employed the electronic colour densitometer designed by Sweet.6 It is to be hoped that either Ansco or some laboratory regularly using Anscocolor will shortly deal with the control of the printing operation in an equally detailed manner. Eastman Color Negative The next integral tripack on the chart has not yet reached us in this country, in fact Eastman Color Negative stock is probably not yet generally available in America, although test rolls have been issued to most of the important laboratories. This eagerly awaited product of the Eastman Kodak Laboratories is the motion picture version of the cut film material known as Ektacolor, which is a material capable of forming its own masking images during colour development— the masking images being designed to compensate for the deficiencies of the dyes which comprise the colour negative image.