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

Page scan 000424 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 #:
000424
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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Nov. 1947 INTERMITTENT MECHANISMS 411 present type of film trap would give the film constant acceleration during the first half of the pull-down and constant deceleration during the last half of the pull-down and yet would not impose a net pull of more than one pound on the film. Let the film be given a constant acceleration of 5000 feet per second per second, the same as the peak acceleration of the Geneva. Then the acceleration curve of the film as compared with that of the Geneva would be as shown in Fig. 3. It can be seen from Fig. 3 that giving the -j .5 Sir * .8 |«0 5,000 Si t, 5,000 il 30 60 PULL DOWN (DEGREES) PULL DOWN (DEGREES) A B FIG. 4. A, Travel, velocity, and acceleration of the film. B, Pull on the film caused by acceleration and film-trap drag. film constant acceleration amounts to chopping off the dotted portion of the Geneva acceleration curve and using it to fill in the cross-hatched portion of the constant film-acceleration curve. The pull-down angle is thus reduced and since the maximum acceleration of the film has not been increased there is no increase in the stress on the film. The reduction in the pull-down angle can be computed from the equation S = Vi of where -5 = — ^5 — = 1/a the height of a frame of film a = 5000 ft /sec2 or 60,000 in. /sec 2s /2X 0.748/2 ^ = \ 60,000 ~ sec 9/2 = 360 X 0.0035 30' 1/24 60° pull-down angle.