We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
380 CINEMATOGRAPHIC ANNUAL
sensitometry which are used to determine the contrast factors (gammas) of development require some correction to take into account the difference between exposures in the sound recording machine, which exposes an element of the film for a very short time to a very bright light, and those usually made in sensitometry; further, account must be taken of the conditions of reproduction, involving the manner in which the reproducing light is focussed on the film and the electrical circuit connecting the photocell to its amplifier.
The lamp current to be used in the recording machine must be determined by test, in order to produce in the film an exposure for the undisturbed light valve such that doubling this exposure when the valve is open to double width (full modulation) shall be just clear of overexposure for the emulsion used and for the development it is decided to give the negative sound record. Unmodulated tracks should be made with various lamp currents, developed all to the chosen contrast and that current determined which results in the density shown on the curve of Fig. 5 corresponding to the ideal negative exposure.
From investigations made for the purpose, it is possible to tabulate appropriate pairs of values of positive and negative gammas and appropriate densities for the unmodulated tracks. The H and D curves are to be obtained from sensitometer strips prepared in the usual way, and these densities are to be measured diffusely. For example if the practice of the release print development involves a positive gamma of 1.75, the proper negative gamma for the sound record is 0.6 and the proper density of the unmodulated negative track is 0.6 referred to the fog density. A density of 0.5 is satisfactory for the unmodulated positive track. These values are accurate for Eastman positive film and are substantially so for the other positive stocks which might be used in recording and in printing.
The limits of permissible modulation of negative exposure when using the light valve can be determined from observation of the valve's own behavior and from a study of the H and D curve. Mechanically the valve moves in exact proportion to the speech currents up to 90% modulation. Photographically, with the lamp current adjusted to give the proper density of the unmodulated track, 90% modulation can be used without driving the negative exposure into the under exposure regions. This