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

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 #:
000497
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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492 FREDERICK E. BARSTOW November of voltage conversion. This would not have been practicable if the voltage requirement had been much above 500 v. Two 220-juf 475-v electrolytic capacitors (C-l and C-2) are conservatively operated in series to give an energy storage of about 12 wsec. Chokes CH-1 and CH-2 both serve to prevent "hold-over" in the flashtube FL-1. A "hold-over" in a flashtube is a continuous glow which occurs if an attempt is made to recharge the capacitors too rapidly. The tube is in a highly ionized state after being flashed Fig. 7. Complete infrared electric-flash instrument recorder, showing power unit, camera and lamphouse assembly, cables and a mock-up of instruments. and, if sufficient current is supplied, the tube will not deionize but will remain conducting and act as a short circuit across the power supply. A choke (CH-1) acts as a high impedance immediately after flashing to limit the current and thus prevent "hold-over." On the other hand, over a period of one second it acts as a relatively low impedance and therefore allows the capacitors C— 1 and C-2 to charge fully before the next flash. An additional choke (CH-2) in series with the flashtube also tends to prevent "hold-over" by causing a