File:The American annual of photography (1922) (14778436211).jpg

Identifier: americanannualof36newy (find matches)
Title: The American annual of photography
Year: 1922 (1920s)
Authors:
Subjects: Photography
Publisher: New York : Tennant and Ward
Contributing Library: Harold B. Lee Library
Digitizing Sponsor: Brigham Young University

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qualities has the added features of speedand latitude. The sensitive coating of the dry plate in accordance withAbney (Treatise on Photography) is prepared as follows:— Pot. Iodide 0-3 gr. in 35 cc of water Pot. Bromide 8.7 40 Nelson No. i Gelatine 2.0 Silver Nitrate 11.4 15 Heinrich Gelatine lo.o or Nelson No. i Gelatine. 6.0 It may be said here that the ingredients as given above arealmost universally used by all plate manufacturers of todayvarying only the ratio of the ingredients so as to insure greateror less speed. The plates employed in Radiography are divided into twodistinct groups—single and double coated. The single coated plate as its name implies has only onegelatine coating, which carries the sensitive salts. For generalwork this probably is the most popularly .known and the mostuniversally employed plate. In work where greater penetra-tion is required, and where owing to a prolonged exposurethe possibility of halation is greatly increased, the double 78 (( ti (( (I
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0. C. CONKLING. 7Q coated plate will be found more advantageous. This plate iscoated with two distinct emulsions—the first one, or the onenearest to the glass, being the absorbing emulsion. It consistsof a surface which is very slow, and as its name implies itsfunction is to absorb the light before it reaches the glass,thus preventing secondary radiation and its natural conse-quence halation. This emulsion when dry in turn is coated with anotherthinner and faster sensitized mixture, which takes care of theweaker rays which strike the surface of the plate. In order to facilitate the handling of the plates, and aboveall keep all metallic substances away from it, the plates as arule are loaded in double envelopes. One the inner is blackand the second the outer orange red. Probably the simplest,and at the same time the safest, method of handHng andloading these envelopes is to place them on the table in pairsred first and black on top with the flaps of the envelopes down.The plate is no

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