File:The American annual of photography (1918) (14594400879).jpg

Identifier: americanannualof1918newy (find matches)
Title: The American annual of photography
Year: 1918 (1910s)
Authors:
Subjects: Photography
Publisher: New York : Tennant and Ward
Contributing Library: Harold B. Lee Library
Digitizing Sponsor: Brigham Young University

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then sep-arated therefrom under water, the blueprint will appear de-veloped and also the same picture will show on the silver pa-per, that is if a positive or a negative both pictures will bepositive or negative respectively. The chemical action is thatthe blueprint sensitized paper acts only on those parts of thesilver paper where the light has converted the potassium fer-rocyanide into potassium ferricyanide, which reduces the sil-ver haloid and produces the reduced silver picture while at thesame time the blueprint is being formed. Silver Prints in Natural Colors The picture is obtained on P. O. P. by only printing a posi-tive from a positive colored transparency, without any devel-oping agent at all in the following manner: A piece of soliopaper for instance which will give very good results, or col-lodion paper is printed on under a colored transparency, suchas a colored lantern slide or a colored Decalcomanie for per-haps twenty-four hours in daylight—somewhat more or less 120
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co ■4-* OhW s CO QO o iz; l-H w does not matter, the time must be left to the judgment of theoperator by looking at the print every now and then whenin the printing frame and by his experience in obtaining thefinal picture. When the print is taken from the printingframe it is of course a very strong negative, graded accordingto the different degrees of light filtered through the differentcolors of the transparency according to their filtering valuesof light, that is where no color or blue, there the picture isdarkest, while where red, it remains light, etc. This negativeprint is n®w printed under a plain glass in a printing frame,without any transparency, and the whites will now turn darkwhile the dark parts will turn darker (or perhaps lighter, thatis more silvery) according to the degree of density. Thiswill only take some minutes and the printing can be observedcontinually until the desired effect is obtained, that is: a pic-ture with the same colors as the original transparency

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