An introduction to the science & practice of photography (1888)
Jones, Chapman · London : Iliffe & Son · leaf 126
122 THE SCIENCE AND PRACTICE OF PHOTOGRAPHY. and warm reception for the new instrument, and it was copied by many opticians of repute, who christened their productions variously as orthoscopic, orthographic, calo- scopic, &c. Fig. 23 shows the lens as made by the … Fig. 23. American optician, Harrison. It will be observed that Petzval has adhered to his first principle of a separated back combination, but in this case the combination is negative or diverging, and therefore makes the focal length of the whole lens longer than that of the front combination.…
Photography
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