An introduction to the science & practice of photography (1891)
Jones, H. Chapman (Henry Chapman), 1854- · London : Iliffe & Son · leaf 145
by first studying a thick double convex simple lens. In fig. 37 the optical centre is indi- cated by a dot, and a b, c d, are rays passing through the optical centre. By continuing within the lens the direc- tion of the rays outside the lens, as is done by the dotted lines, two points are obtained… … Fig. 38. owe their existence to the thickness of the lens. In esti- mating the focal length of such a lens by taking a quarter of the distance between an object and its image produced of equal size, we get too high a result, because the dis- tance between the points of admission and emission is not…
Photography
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