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 #:
000376
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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1949 LENS-CALIBRATION REPORT 373 The light used in making the determination shall be white, * and the sensitivity characteristic of the photoelectric receiver shall approximate that of ordinary panchromatic emulsion, t It is not considered that these factors are at all critical, and that no closer specification than this is necessary. Obviously errors will arise if the light transmitted by the lens has a strongly selective transmission, but such lenses would be undesirable for other reasons. The incident light shall fill a field not exceeding 10 degrees more than the angular field of the lens itself. During measurement, the light shall traverse the lens in the direction normally employed in photography. The lens should be carefully examined before calibration to ensure that there are no shiny regions in the barrel which would lead to flare or unwanted stray light, since this would vitiate the measurements badly. The lens surfaces should of course be clean. XII. CORNER-TO-CENTER RATIO Having calibrated the stop markings of the lens on the T system, the observer may, if desired, determine in addition the ratio of corner illumination to center illumination, at full aperture and preferably at other apertures also. For this purpose the 3-mm (or IVa-mm) hole shall be used first at the center of the field, and then moved outwards until its rim is touching the top and side limits of the camera gate. This distance is shown in Table I. TABLE I Gate, Mm Radial Shift of Hole, Mm 35(16.03X22.05) 16 ( 7.47 X 10.41) 8( 3.51 X 4.80) 11.5 4.5 2.0 The corner-to-center ratio of illumination so determined will take care of cos4 and vignetting effects within the lens. XIII. EXTENDED SOURCE METHOD OF T-STOP CALIBRATION This method of lens calibration has been described by Gardner13 and Sachtleben, 9 the underlying theory being given by McRae. 4 It is based * Specifically a tungsten filament lamp operating between 2900 and 3200 degrees Kelvin. t A suitable cell is one having an S-3 surface, combined with a Corning 9780 glass filter about 2.5 mm .thick.