Transactions of the Society of Motion Picture Engineers (1916)

Record Details:

Title:
Transactions of the Society of Motion Picture Engineers
Date:
1916
Publisher:
Washington D.C. : Society of Motion Picture Engineers
Volume:
Society of Motion Picture Engineers : incorporation and by-laws (1916)
Leaf #:
000262
Language:
English
Subjects:
motion pictures, Cinematography -- Periodicals
Collection:
Technical Journals
Format:
Periodicals
Contributor:
Library of Congress, MBRS, Moving Image Section
Sponsor:
Library of Congress, Motion Picture, Broadcasting and Recorded Sound Division
Coordinator:
Media History Digital Library
Description:
Preceeded by an unnumbered issue published in 1916 called: Incorporation and by-laws
Date Added:
December 28, 2023
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m^^ Fig. 2 The candle power in the direction of the Photometer is not changed by partially :surrounding the light source with a non-reflecting surface. already been stated, it is obvious that when the photometer is balanced it will indicate an intensity of i candle. In the second case, (Fig. 2B) we have used a sphere with a much smaller opening and are, therefore, wasting still more of the light, but even in this case our photometer will indicate an intensity of i candle. In fact, our reading will be i candle regardless of the size of the opening, that is, regardless of the quantity of light we allow to be emitted, provided the direct rays from the candle to the photometer are not obstructed. This leads us to the important conclusion that the candlepower of a source gives no indication of the total quantity of light emitted by that source. Candle-power, we may say, is analogous to a measurement of the depth of a pool of water at a certain point on its .surface — a measurement which is useful for certain purposes, but in itself gives no indication of the quantity of water in the pool. The first fundamental concept we have to deal with in illumination, then, is candle-power, which is the measure of strength of a source to produce illumination in a given direction, and the power in a horizontal direction of a candle made according to certain specifications and burning under certain conditions has been arbitrarily chosen as the unit for measuring this strength. 76