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Modern Motion Picture Film
Laboratory Practice By |. D. WRATTEN
Delivered to a meeting of the British Kinematograph Society, held at the Gaumont-British Theatre, Film House, 142, Wardour Street, W.1, on Monday, September 2Ist, 1936
SYNOPSIS
This paper deals with the
following points :—
1. The importance of sensitometers and densitometers.
2. The use of variable lamp current for sound track recording, together with a standard developing time to secure correct sound track density.
3. The use of test strips when processing positive prints and the comparison between American and English gamma values.
4. Various developing formule and the difference in development speed for picture and sound negatives.
5. Two main types of release printers.
6. Automatic light control printers
employing air pressure.
. The “ Cinex”’ sensitometer.
. Developing machines.
. The elimination of directional effects and the electric regeneration of fixing baths
10. Negative and print examination.
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HE purpose of this paper is to discuss af some of the methods and equipment used in the laboratories of England and the U.S.A. for the processing of motion picture film. It must be remembered, howaver, that laboratories vary considerably in regard to capacity, some having an output of 100,000 feet or so weekly, while others have output requirements running into millions of feet per week. It follows, therefore, that methods and equipment considered essential to a large laboratory may not necéssarily be required by the smaller laboratory.
Sensitometers and Densitometers In many of the smaller laboratories the development of positive prints is still con
trolled “by the personal judgment of the man in charge of the department. By varying the time of development within certain limits, the machine operator attempts to compensate for developer exhaustion and also for small errors in
HKG:
printer grading Most of the larger laboratories, however, control the negative developer and the positive film development by sensitometric means, and since photographic sensitometry occupies such an important part in the modern laboratory, it will be worth while, perhaps, to discuss very briefly the sensitometric apparatus required and its application to the development of picture negative, sound negative, and ‘positive prints.
The equipment required consists of a machine capable of impressing on the film to be used an accurately pre-determined scale of exposures which can be maintained constant from test to test over a very long period of time, and an apparatus for measuring the densities resulting from development of the film bearing the series of exposures. These instruments are known as the Sensitometer and the Densitometer respectively. The sensitometer