How to add sound to amateur films (1954)

Record Details:

Title:
How to add sound to amateur films
Date:
1954
Publisher:
London : Focal Press
Volume:
How to add sound to amateur films
Leaf #:
00093
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Niles Essanay Silent Film Museum
Sponsor:
Media History Digital Library
Coordinator:
Media History Digital Library
Description:
Date Added:
March 28, 2024
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Synchronisation from the Mains An exactly constant projector speed will give accurate synchronisation only if the speed of the magnetic recording is always the same. In the majority of tape recorders, the capstan is driven by an induction motor. The speed of this varies with mains frequency and, to a lesser extent, with mains voltage. On the other hand, the governed-speed motor in a sound-on-film projector may be influenced primarily by temperature. So what you record and reproduce successfully one day may not keep in step next time you try it. This may be because the magnetic recorder speed has changed though the projector speed has not. A few sound-on-film projectors use an induction motor instead of the more usual mechanically-governed type. This behaves in much the same way as the recorder motor, and so gives rather better synchronisation. When the mains frequency rises, the speed of film and tape (or wire) increases in almost the same proportion and they keep fairly well in step. By painting in alternate spaces, as at A, you can use these patterns to provide stroboscopes of 64, 60, 56 and 52 bars, reading from outside to centre. By painting in alternate pairs of spaces, as at B, you get 32, 30, 28, and 26 bars. Painting in alternate groups of four spaces, as at C, you can use the same patterns to provide 16, 15, Hand 13 bars. 89