Photographic optics and colour photography : including the camera, kinematograph, optical lantern, and the theory and practice of image formation (1909)
Johnson, G. Lindsay (George Lindsay), 1853-1943 · New York : D. Van Nostrand Co. · leaf 107
tional Physical Laboratory. Take any two well-defined obj ects, such as a couple of telegraph posts which are situated at 00 . Infinity in photographic optics signifies any distance you please at which an object is placed when its image lies in the same plane as the principal focus ; in other… … and measure their distance apart with a micrometer gauge or fine compasses on the screen. This length divided by the tangent of the angle will give the true focal length of the lens, or F = tan vl Thus, let AB be the two objects (Fig. 65) which subtend an
Photographic optics · Color photography
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