File:The American annual of photography (1922) (14781353062).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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mulsions and should be compared on repre-sentative emulsions in such classes as follows: r NC film. Negative emulsions ( Commercial film ( Process film. ^ . . - . ( Positive motion picture film. Positive emulsions i ^ , t . 1 ( beed Lantern plates. Paper emulsions \ ^ , . ^ . I Bromide and Artura Iris. Mixing the Developer When compounding test developers from the solid develop-ing agent, it is important to weigh out the various ingredientsvery carefully in order to insure an accurate comparison. In-stead of weighing out small quantities of potassium bromideit is more accurate to measure out the required volume of a10% solution. Since a developerwhich gives bad chemical fog is useless,and since more developers are rejected on account of fog thanfor any other defect, it is important that the rules of mixingdevelopers be carefully observed so that no fogging agentsare produced during mixing. As a general rule, the sulphiteshould be dissolved first, each chemical thoroughly dissolved 186
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in o 1—1 187 before the next one is added, and the developer mixed at aslow a temperature as possible; otherwise, the developer willgive fog even if prepared from the purest chemicals. A reporton a developer incorrectly mixed is absolutely worthless, be-cause there is no way of telling whether the fog was inherentin the developer or was a result of incorrect mixing. To mix the standard formula on page 185 proceed as follows:Dissolve the sulphite in about 300 cc. or 10 oz. of luke warmwater; then add the Elon or hydroquinone or both, and allowto cool. Meanwhile, dissolve the carbonate in 300 cc. of lukewarm water, add the bromide, and cool. Now add the car-bonate solution to the sulphite solution and add cold water tomake 32 oz. or i liter. Sensitometric Methods. When we expose a plate or film in a camera focused on alandscape, we impress upon the emulsion areas of light ofvarying sizes and of varying brightness. After developmentthe negative consists of areas of varying sizes and va

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