Principles of cinematography : a handbook of motion picture technology (1953)

Page scan 000326 from Principles of cinematography : a handbook of motion picture technology

Record Details:

Title:
Principles of cinematography : a handbook of motion picture technology
Date:
1953
Publisher:
London : Fountain Press
Volume:
Principles of cinematography : a handbook of motion picture technology
Leaf #:
000326
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
Date Added:
May 15, 2025
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322 PRINCIPLES OF CINEMATOGRAPHY Fig. 141.— The design of sprocket teeth. under these conditions, all the load is taken by the leading sprocket tooth, that is, tooth No. 1 or the tooth from which the film is just about to strip as the sprocket rotates in the direction indicated by the arrow. Obviously, any argument applied to a sprocket rotating in this manner, that is, acting as a pulling sprocket, will be equally true when the sprocket rotates in the opposite direction and acts as a hold-back sprocket. Although the film is only driven by tooth No. 1, its speed will be equal to that of the sprocket over that period during which it is well seated down at the base of the tooth. Immediately the film commences to strip from the tooth and, therefore, to ride up the curved tooth face, its speed will be slower than that of the sprocket and will remain in this condition until the following tooth and perforation come into contact. It must be understood that by saying 'a speed difference will exist' we mean a difference in angular speed since, of course, the linear speed of the upper film surface must, under all conditions, be greater than the linear speed of the base side which is in contact with the root of the sprocket tooth. The actual, or linear speed of the film is given by the equation: V = ttN (D + t) Where V = the film velocity, N = number of sprocket revolutions per second D = sprocket diameter at the base circle, t = the film thickness.