Practical cinematography and its applications (1913)

Page scan 000145 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 #:
000145
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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io6 PRACTICAL CINEMATOGRAPHY of a very severe character. Moreover, curiously enough, under the illumination of the ray of light the erratic movements of the blade appear to be three or four times more severe than they really are. But as the motor revolutions and the tuning- fork vibrations are brought into synchrony, the movements grow quieter, until at last the tuning- fork once more appears to be quiescent. The explanation of this quasi-cinematographic illusion, which is as interesting and as puzzling as that of the wheel, is very simple, for it is based indeed upon the same phenomena. As the card- board disk is provided with two small holes spaced 180 degrees apart, the passage of the ray of light is intercepted by the opaque section of the disk 80 times per second when the motor revolutions and the tuning-fork vibrations are in absolute synchrony. The result is that at this speed the light strikes the tuning-fork each time at the instant it is at the half-way point in its oscillating travel. One hole in the disk comes before the light when the blade has completed half its move- ment in one direction, while the second hole comes into line with the light when the blade is at the same point on its return journey. Con- sequently the light falls upon the blade at the same spot every time, causing the eye to imagine that it sees the blade always in the one position as if under a steady ray of continuous light.