A manual of photographic chemistry, theoretical and practical . n of the two retinas not correspond-ing. From the same cause, on first trying to fix the two eyeson the two wafers, they appear double until the optic axis ofeach eye (or a line of indefinite length drawn through thecentre of the pupil from the central and most distinctly see-ing part of the retina) is directed fully to each wafer. Whenthis is the case a similar picture falls on similar parts ofeach, and the two objects are perceived by the mind as other less distinct images, one on each side of the prin-cipal one, are due
A manual of photographic chemistry, theoretical and practical . n of the two retinas not correspond-ing. From the same cause, on first trying to fix the two eyeson the two wafers, they appear double until the optic axis ofeach eye (or a line of indefinite length drawn through thecentre of the pupil from the central and most distinctly see-ing part of the retina) is directed fully to each wafer. Whenthis is the case a similar picture falls on similar parts ofeach, and the two objects are perceived by the mind as other less distinct images, one on each side of the prin-cipal one, are due to each eye perceiving its neighborswafer, but on points of the eyes that do not correspond. The cause of the combined image standing out in front orbehind the paper is due. to the mind always referring theplace of an object to the point where the optic axes meet, THE STEKEOSCOPE. 355 and when the two wafers are united by squinting, this point isin front, and when by distant focusing, behind the will be evident from the diagrams on preceding Fig. 51. Fig, 49 represents union by squinting ; the optic axis ofeach eye is directed to the opposite wafer, and the image isreferred by the mind to P in front, where the axes cross. shows the ordinary way of viewing with the stereoscope,
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Keywords: ., bookcentury1800, bookdecade1880, bookidma, booksubjectphotography
