Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . coincidence in the direction ofrays before and after transmission is found in thepin-hole camera, of which more anon. So far for the first condition of non-distortion ;but there is yet another. The pencils transmitted must be such as wouldhave met, if not refracted, at a common reason of this is obvious after a little an image were formed by the action of pencilswhich were emitted toward different termini, it would suffer distortion, like
Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . coincidence in the direction ofrays before and after transmission is found in thepin-hole camera, of which more anon. So far for the first condition of non-distortion ;but there is yet another. The pencils transmitted must be such as wouldhave met, if not refracted, at a common reason of this is obvious after a little an image were formed by the action of pencilswhich were emitted toward different termini, it would suffer distortion, likethat of a perspective drawing made not from one but from many points of Now, let us see how we get rid of these beautiful colors, which we admire so much inthe rainbow and the glittering dewdrop, but which hurt the eye of an optician in anoptical instrument. If a ray of white light, R (Fig. 32), falls obliquely on a parallelplane glass, it is decomposed as soon as it enters the glass; but on the other side allthe colored rays which made white light are, on leaving the glass, parallel to theirformer direction. Fig. 32. Fig. But if a prism, A (Fig. 33), is struck by an oblique ray, R, the ray is dispersed in theglass, and the colored rays leave the prism diverging, and they cannot be properly mixedagain to white light, except we can give to the leaving rays their parallelism again.
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Keywords: ., bookcentury1800, bookdecade1880, bookidwilsonsquart, bookyear1887
