A manual of photographic chemistry, theoretical and practical . e, is more of a full face than Fig. 46,which, being viewed from a point removed a little to the left,partakes of the character of a profile. The human eyes are placed about 2|- inches, or from that to2|- inches, asunder; hence it follows that, the points of sightbeing separated, a dissimilar image of a solid object is formed THE STEREOSCOPE. 353 on the retina of each eye. We did not however see two images,but a single one, which is stereoscopic. In looking at a picture painted on a flat surface the case isdifferent; each of the ey
A manual of photographic chemistry, theoretical and practical . e, is more of a full face than Fig. 46,which, being viewed from a point removed a little to the left,partakes of the character of a profile. The human eyes are placed about 2|- inches, or from that to2|- inches, asunder; hence it follows that, the points of sightbeing separated, a dissimilar image of a solid object is formed THE STEREOSCOPE. 353 on the retina of each eye. We did not however see two images,but a single one, which is stereoscopic. In looking at a picture painted on a flat surface the case isdifferent; each of the eyes, as before, receives an image, butthese images are in every respect similar; consequently theimpression of solidity is wanting. A single picture, therefore,cannot be made to appear stereoscopic. To convey the illu-sion, two pictures must be employed, the one being a right andthe other a left perspective projection of the object. Thepictures must also be so arranged, that each is presented to itsown eye, and that the two appear to proceed from the Fig. 46. Fig. 47. I^The reflecting stereoscope, employed to effect this formsluminous images of the binocular pictures, and throws theseimages together, so that, on looking into the instrument, onlya single image is seen, in a central position. It should, how-ever, be understood, that no optical arrangement of any kindis indispensably required, since it is quite possible, with a littleeffort, to combine the two images by the unaided organs ofvision. The following diagram (Fig. 48) will make thisobvious : Fig. 48. The circles A and B represent two wafers which are stuckon paper at a distance of about 1|- inch from each other. Theyare then viewed, either by squinting strongly, until the righteye looks at the left wafer, and the left eye at the right wafer, 354 BINOCULAR PHOTOGRAPHY. or else by focusing the eyes for a distance beyond the wafers,which is easily effected by looking at a point midway between,but giving attentio
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Keywords: ., bookcentury1800, bookdecade1880, bookidma, booksubjectphotography
