Snelling, Henry Hunt, 1816-1897 · [New York : W.B. Smith] · leaf 357
as it were stamped with theirdegree of sensitiveness until we want toapply them to test the power of two lenses.The impression is made on one-half of theplate, leaving the other half for the imageof the dynactinometer. After having operated in the two came-ra-obscura, each supplied with the… … The number of spots given by the pho-tographometer, Fig. 47, will indicate thesensitiveness of the plate ; and in compar-ing the two images given by the dynacti-nometer, accounting for the difference ofsensitiveness of each plate, if there is anyrwe are able at once to determine the com-parative…
Photography · Art and photography
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![An illustration from [Graphophone patents] (1878)](https://img.insideoutlibrary.com/img/200/ia-graphophonepaten07unit-147-115.webp)
