Cinematographic annual : 1930 (1930)

Record Details:

Title:
Cinematographic annual : 1930
Date:
1930
Publisher:
Hollywood : The American Society of Cinematographers, Inc.
Volume:
Cinematographic annual : 1930
Leaf #:
000407
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
{"Media History Digital Library","Richard Koszarski","Jeff Joseph"}
Coordinator:
Media History Digital Library
Description:
Date Added:
March 21, 2024
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REPRODUCTION IN THE THEATRE 387 <3(D>t ^3d> EXCITING LAMP FILM PLANE ^ SLIT ;ggS:Mix. WIDE x 3/ 16" LG. VJ APPROX. 41/4' LIGHT BEAM .ooiM i;ggg;. WIDEX 1/8" LONG AT FILM PLANE LENS TUBE DIAGRAM FIGURE 4 to the film as a very narrow beam one mil in width. It is necessary that this beam be very narrow as the highest reproducible frequency depends upon the speed of the film and the narrowness of the light beam falling on the sound track. The photoelectric cell on which the light falls after passing through the sound record is shown in Fig. 5. Film reproduction is made possible through the use of this photoelectric cell or one having similar characteristics, that is, a cell capable of emitting elecrons at a rate proportional to the incident light within certain predetermined limits. This cell consists of two electrodes, one a photoactive metal and the other the sole function of which is that of an electric conductor. The photoactive metal most used for the purpose of sound reproduction is potassium. However, other alkali metals have been used. A polarizing voltage is placed across the terminals of the photoelectric cell through such a high resistance that in operation there is obtained from the cell a voltage across this resistance which is proportional to the incident light. This cell may be thought of simply as a resistance which varies directly with the quantity of light falling on the cell. FIGURE 5