Practical cinematography and its applications (1913)

Page scan 000142 from Practical cinematography and its applications

Record Details:

Title:
Practical cinematography and its applications
Date:
1913
Publisher:
Philadelphia, Lippincott
Volume:
Practical cinematography and its applications
Leaf #:
000142
Language:
English
Collection:
Books
Format:
Books
Contributor:
Gerstein - University of Toronto
Sponsor:
MSN
Coordinator:
Media History Digital Library
Description:
14
Date Added:
July 19, 2022
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ABERRATIONS OF PHOTOGRAPHY 103 Monsieur Bull discovered another curious optical illusion produced by the moving wheel. Still taking the four-spoke wheel as an illustration, we will suppose that between each exposure the spokes are displaced a little more or a little less than half the angle between them. As the spokes are set 90 degrees apart, the half-way point will be 45 degrees. When a succession of such pictures is thrown upon the screen, it is not four spokes which are seen, but eight (Fig. 7). Monsieur Bull is engaged upon a series of experi- ments to ascertain why this peculiar optical illu- sion should prevail, and the explanation will prove interesting. Another interesting and more conclusive illustration of the optically illusory properties of the cinematograph was demonstrated to me by Monsieur Bull. In order to be absolutely positive that an apparatus which he uses in certain cinematographic investigations should maintain the speed he desires, he has contrived a tuning-fork control for his electric motor. This tuning-fork resembles a large trembler blade, such as is used in the high-tension accumulator and coil ignition system upon motor cars. This particular instrument is timed to make, say, 40 vibrations per second, and at this speed, of course, it emits a distinctive musical note. This tuning-fork controls the electric motor driving