Snelling, Henry Hunt, 1816-1897 · [New York : W.B. Smith] · leaf 354
zone had attained the first coating of yellowcolor ; a second zone had reached the red—a third the blue and green—and a fourthhaving passed through all these tints, hadobtained the second yellow coating. Thenumber of white circular spots on eachvertical zone indicates the degree of sensi-tiveness… … strument, and strained over two rollers, r,r, it will be evident that the sensitiveplate is screened from light until the move-able slide falling down the inclined planepasses over it. The openings in this move- increased whiteness of the spots correspond-ing with the holes, each four vertical…
Photography · Art and photography
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