Society of Motion Picture Engineers : incorporation and by-laws (1927)

Page scan 000155 from Society of Motion Picture Engineers : incorporation and by-laws

Record Details:

Title:
Society of Motion Picture Engineers : incorporation and by-laws
Date:
1927
Publisher:
New York : Society of Motion Picture Engineers
Volume:
Transactions of the Society of Motion Picture Engineers (1927)
Leaf #:
000155
Language:
English
Subjects:
motion pictures, Cinematography -- Periodicals
Collection:
Technical Journals
Format:
Periodicals
Contributor:
Library of Congress, MBRS, Moving Image Section
Sponsor:
Library of Congress, Motion Picture, Broadcasting and Recorded Sound Division
Coordinator:
Media History Digital Library
Description:
Preceeded by an unnumbered issue published in 1916 called: Incorporation and by-laws
Date Added:
September 12, 2024
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Light Filters — Jones 145 photometric density curve of a yellow (blue absorbing) gelatine filter. Curve B shows the same characteristic for a blue-green (red absorbing) gelatine filter. Curve C is that obtained by adding the ordinates of A and B and shows the spectral absorption obtained by the superposition of one layer of each filter. Curves A and B intersect at the point p of which the density value is 0.25 (transmission =56.4%). The density of the superposed combination, curve C, at the corresponding wave-length is two times 0.25 or 0.50 30 2.5 2.0 z u o 1.0 0.5 -in • / 300 400 600 700 500 WAVELENGTH (m/i) Fig. 5. Spectrophotometric density curve of "sharp cut" green filter. (transmission = 32%) . This is the minimum density value of C. Hence at the wave-length which is transmitted most freely by the combination only 32 per cent of the incident radiation is transmitted. This compound filter (curve C) is bright green in color and isolates fairly well the wave-length band from 500 to 600 mfx. A filter of much greater efficiency for this purpose can be made by incorporating properly selected dyes in a gelatine film. Such a filter is illustrated by the curve in Fig. 5. This has maximum transmission at approximately the same wave-length as C (Fig. 4) this being 54 per cent (D = 0.25), ahnost twice that of filter C. A similar low efficiency is usually encountered to a greater or lesser extent whenever an attempt is made to isolate some particular