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

Page scan 000104 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 #:
000104
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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JOURNAL OF THE SOCIETY OF MOTION PICTURE ENGINEERS Vol 49 AUGUST 1947 No. 2 PHOTOMETRIC CALIBRATION OF LENSES R. KINGSLAKE* PREFACE During the past few years there has been a rapidly growing need for a more accurate expression of the photographic speed of a lens than is afforded by the simple /-number ratio. The density of a photographic image depends on (a) the brightness of the subject, (b) the effective speed of the lens, (c) the speed of the film, and (d) the exposure time. In modern motion picture photography, all these factors except (b) are controlled and known to within a few per cent, but the supposed speed of the lens may be in error by as much as 60 or 70 per cent. This is caused by light lost by surface reflections or by direct absorption in the lens, and to incorrect marking of the /-number scale. For this reason the SMPE Standards Committee has recently set up a Subcommittee on Lens Calibration to study the whole subject and to recommend a standard procedure for measuring the effective photographic speed of a lens. The Subcommittee will also attempt to standardize a new system of speed markings which eventually will replace entirely the /-number markings that have heretofore been the only indication of lens speed. The urgency of this problem is borne out by the fact that since 1941 no less than five papers have appeared in the SMPE Journal dealing with lens calibration, and three more similar papers are being published in the present issue. The new Subcommittee contains seven members from the West Coast, to represent the Hollywood interest, and seven members from manufacturing firms in the East and Middle West and from the National Bureau of Standards. * Chairman, Lens Calibration Subcommittee. 95