An introduction to the science & practice of photography (1895)
Jones, Henry Chapman, 1854- · London, Iliffe, Sons & Sturmey Ltd · leaf 84
etimes V7 v LA Li Fig. 12. called concavo-convex, but this name is needlessly confusing to the student. Disregarding for the moment the spherical and chro- matic aberrations that such lenses suffer from, we can sum up the effects that can be produced by their means in a useful and simple way. If a… … Fig. 13. point is the " focal point," or, more correctly, " the princi- pal focal point," and its distance from the lens is the " focal length " of the lens employed. In this, as in every other case, the refracting effect of the lens is the same whichever way the light travels through it, so that…
Photography
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