Lummer, O. (Otto), 1860-1925, Thompson, Silvanus P. (Silvanus Phillips), 1851-1916 · London, New York, Macmillan and Co., 1900 · leaf 149
129 COMPUTATION OF LENSES Ill is to be measured. For axial rays CL2 is equal to EL^, because of the smallness of the angle X.,. For the rays of greater zonal distance CL^ is … Fig. 55. greater than EL.,. The next stage in the computation is to reckon out these two magnitudes for the three rays chosen to be computed. From the triangle CEL^ it follows that CE EL.,= tan A., CE " CL.,= sin A., Let EL., be called F (the true focal length), and CL, be called G (the focal…
Photographic optics
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