We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
194 THE ADVANCE OF PHOTOGRAPHY
on experimental work, and of producing results which have a more pleasing effect, and certainly appeal more to the artistic eye than the more rigidly correct prints obtained with ordinary P.O. P. or bromides.
Some of these, such as the Carbon process and the Gum Bichromate Printing,1 depend upon the action of light on bichromates in contact with a colloid substance and a pigment on paper (see p. 81).
The Ozobrome 2 process is another which differs from the ordinary carbon process in that the worker is independent of daylight for printing — in fact, this is often spoken of as the evening carbon process, since no direct action of light is required.
By this method a number of copies in carbon can be obtained from one bromide print Avithout using a negative, and in the end the original bromide print, if it has been carefully handled, may still remain unimpaired.
For the ordinary worker there are papers which can be used for obtaining prints by daylight (P.O.P.), and others which it is best to employ when a reliably constant source of artificial light can be obtained.
Toning and Fixing. — P.O. P. is the contraction commonly used for Gelatino-Chloride printing-out paper. This is paper coated with an emulsion in gelatine of silver chloride and other silver salts . These papers, when exposed under a negative, become darkened by the action of the light which passes through, and thus a positive image of the object is obtained. These images, of course, if exposed to light after removal from beneath the negative, would soon be lost sight of, since the whole sensitized surface would gradually become darkened. Hence some means must be taken to fix the print, and for this purpose hypo is again used,
1 See J. C. S. Mummery, Photo. Journ., 1904, and C. Wille, Photo. Journ., 1908 (May).
2 T. Manly, Photo. Journ., 1908 (June). Booklet by Ozobrome Ltd., Kentish Town, N.W.