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Antoine Claudet
The Focimeter
1853
Book illustration
Google Books
LL/34651
Published in "Part II - Scientific Investigations on Photography" in "A Manual of Photography" (Third edition) by Robert Hunt (London: John Joseph Griffin & Co., 1853), a part of the "Encyclopeadia Metropolitana: or, System of Universal Knowledge". P.159
M. Claudet has also devised a very ingenious instrument for focusing, which he calls his Focimeter. (Fig. 24.) This it will be seen from the accompanying woodcut consists merely of segments of a circle, numbered and placed at fixed distances apart, upon a moveable axis. This is copied by the camera on a plate or paper, and the result is shewn in the annexed figure (25), in which it will be seen different degrees of effect are supposed to have been produced. These determine the best focal point for any lens very readily, and it is really a most useful piece of apparatus in the hands of the photographer.
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