Snelling, Henry Hunt, 1816-1897 · [New York : W.B. Smith] · leaf 355
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… … 47 having been exposed for the same time tosolar influence. THE FOCIMETER. Mr. Claudet has also devised a very in-genious instrument for focusing, which hecalls his Focimeter. (Fig. 49.) This it
Photography · Art and photography
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