Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . h an angle of 90°, the eyemust be placed, with considerable accuracy, at a distance from the picture equalto one-half itf^ width, else the amount of distortion may be considerable. We will now consider the case of photographing a row of houses, of equalsize, with a wide-angle lens. The camera is supposed to be opposite the centralhouse, with the plate parallel to the row. It is objected that the resultingpicture will give the houses all of the same size, when we
Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . h an angle of 90°, the eyemust be placed, with considerable accuracy, at a distance from the picture equalto one-half itf^ width, else the amount of distortion may be considerable. We will now consider the case of photographing a row of houses, of equalsize, with a wide-angle lens. The camera is supposed to be opposite the centralhouse, with the plate parallel to the row. It is objected that the resultingpicture will give the houses all of the same size, when we measure them on theplate. After what has been said about the necessity for placing the eye in the rightposition, a little consideration will show this is as it should be, for the properperspective effect is produced by the picture itself, the extreme houses in thepicture being more distant from the eye than tlie central one, in the same pro-suited to the material of which it is made ; for our present purpose, both of the lensesmay be made of the same glass, but it is much better if the lens M is made of a denser Fig 2G. M ^ A. glass, as we shall soon see, that the same lens may be used to correct the chromatic aber-ration also. By this method the spherical aberration can not only be corrected, but themarginal rays can be made to cross the axis farther from the lens than the central ones;in this case the lens is called over-corrected, wliile if not enough corrected, it is calledunder-corrected. So far we have considered the aberration of rays parallel with the magic lanterns, photographic and microscopic lenses include angles from 40° to 175,and the foregoing is only applicable to a narrow angle near the centre of the lens. If alens, corrected, parallel to its axis, for spherical aberration, is struck obliquely by parallel 4 50 WILSONS QUARTER CENTURY IN PHOTOGRAPHY. portion as when viewing the houses themselves from the point where the viewwas taken. It is for the r
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Keywords: ., bookcentury1800, bookdecade1880, bookidwilsonsquart, bookyear1887
