Journal of the Society of Motion Picture Engineers (1930-1949)

Page scan 000188 from Journal of the Society of Motion Picture Engineers

Record Details:

Title:
Journal of the Society of Motion Picture Engineers
Date:
1930-1949
Publisher:
New York, N.Y. : The Society
Volume:
Journal of the Society of Motion Picture Engineers
Leaf #:
000188
Language:
English
Collection:
Technical Journals
Format:
Periodicals
Contributor:
Prelinger Library
Sponsor:
MSN
Coordinator:
Media History Digital Library
Description:
The Journal of the Society of Motion Picture Engineers (SMPE)Êdocuments the technological progress of the film industry, highlighting technical developments in production and exhibition. Of special interest are articles about special effects, theater practices, lighting, and the introduction of the 16mm format. Initially titled "Transactions of the Journal of the Society of Motion Picture Engineers."Digitized by the Prelinger Library and the Library of Congress Motion Picture, Broadcasting and Recorded Sound Division.
Date Added:
July 19, 2022
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A PHYSICAL DENSITOMETER 181 light but that passing through the film reaches the cell. The photoelectric cell current is registered by a Weston model 440 microammeter with a 30-microampere range. A suitable shunt is placed across the meter to provide the desired damping. The characteristic of the cell is such that greatest efficiency is attained when using a low load resistance. For this reason a model 440 is preferable. The scale of the meter is calibrated in density from 0 to 1.0, which is sufficient for reading sound-track densities and sound negative gammas of the variable -density type of processing. FIG. 1. The densitometer fitted to the examining bench. In operation, the light falling upon the cell in the reading position is adjusted to register zero density on the meter without any film over the aperture. After this adjustment all that is required is to place the film over the aperture and read the density indicated by the meter. The device is calibrated in two ways. With low load resistance, the cell current increases linearly per unit of light intensity over a large range of intensity Therefore, using a diffused light source, the relation between current and diffused film transmission will also be linear (Fig. 3). Hence by measuring known densities with the cell and calculating the densities from the current vs. transmission curve, a calibration of the device is obtained. A secondary check is made by