Motion picture handbook; a guide for managers and operators of motion picture theatres ([c1916])

Record Details:

Title:
Motion picture handbook; a guide for managers and operators of motion picture theatres
Date:
[c1916]
Publisher:
New York City, The Moving Picture World
Volume:
Motion picture handbook; a guide for managers and operators of motion picture theatres
Leaf #:
000316
Language:
English
Collection:
Books
Format:
Books
Contributor:
University of California Libraries
Sponsor:
MSN
Coordinator:
Media History Digital Library
Description:
Date Added:
July 19, 2022
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FOR MANAGERS AND OPERATORS 297 When we consider the alternating current arc, however, we encounter an entirely and a radically different proposition; also one which is more difficult to handle where less than 70 amperes are used. As already explained, the crater will form on both carbon tips when A. C. is used, since each carbon is alternately positive and negative many times each second. As has already been set forth, the amount of available projection light will, within certain limits, be in direct proportion to the area of the crater, how squarely it can be made to face the condenser, and kind of current. With the crater-producing force divided between two carbons, as is the case with A. C., it follows that neither crater will be as large, for a given number of amperes, as would be Figure 124. the case with D. C., with which the whole crater making force is centered on one carbon. It is even true, as I have already said, that both A. C. craters combined will not equal the area of one D. C. crater, where equal amperage is used. It has long since been very generally accepted as a fact, however, that, due to optical difficulties, it is neither feasible nor good practice for operators projecting with A. C. to use both craters. Operators who study the details of projection have long since come to the conclusion that a more uniformly excellent result will be had by using only one A. C. crater, the upper, of course. One effect which almost certainly follows an attempt to use both craters is a double spot at the aperture,