Transactions of the Society of Motion Picture Engineers (1925)

Record Details:

Title:
Transactions of the Society of Motion Picture Engineers
Date:
1925
Publisher:
New York : Society of Motion Picture Engineers
Volume:
Transactions of the Society of Motion Picture Engineers (1925)
Leaf #:
000495
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:
November 10, 2022
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Rack Marks and Airhell Markings — Crabtree and Ives 97 This grading of density from top to bottom of the rack is due to the fact that wherever development occurs reaction products consisting of oxidized developer and sodium bromide are formed. These substances are strong restrainers of development and have a greater density or specific gravity than the fresh developer and therefore tend to flow downward, while developer flows from above to take its place. As the developer flows down the vertical film it becomes gradually more and more exhausted because it has assisted in developing the upper portions. This results in a gradual diminution in the degree of development of the film from top to bottom of the rack. The actual existence of convection currents in a vertical developing tank has been shown by Bullock/ who placed paper fibres in the WiTTiO ^^^ ^ m ♦ ^ m • # # ♦ • # Fig. 2. Streaks caused by the Restraining Action of the Products of Development solution. During development the fibres were observed to travel downwards along the film and then upwards at the side of the tank. The restraining effect of the reaction products of development may be very clearly demonstrated by exposing a strip of film through a metal plate punched with a number of holes, slightly flashing the whole film to light and then placing the film vertically in the developer without agitation. Immediately below each black circle which develops up, a white tail is produced as shown in Fig. 2 caused 1 "On the Convention Effects in Photographic Bathing Operations in the Absence of Agitation," by E. R. Bullock, B J. Phot., Feb. 1922, p. 110.