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Stellar

stereoscopic, image, seen, images, positive and colors

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STELLAR PHOTOORAPHY.—See Asti-Gnomical. Photography.

form of stereoscope which enables reproductions of objects to be seen stereoscopically, in their natural colors. It consists primarily of an ordinary stereo scope, such as everybody is familiar with. The two stereoscopic images, placed axially to the oculars, are viewed by means of colored screens, the one by a translucent red glass, the other by blue. It should be said that the positive chromograms are reproduced in the same way as is re quired for examination in the photochromoscope of Mr. Ives, that is, each one only reproduce certain color sensations. It is necessary, in order that the synthesis of the colors should be complete and satisfactory, there should be a combination of three images, so that, in addition to the red and blue, it becomes necessary to have a green positive. Of course, the two vertical stereoscopic images have the same differences as regards points of view and inclusion of subjects as characterize ordinary stereo graphs. The third image is placed horizontally in the base of the stereoscope at right angles to one of the vertical images. An opening in the base permits the light reflected from the mirror C D to traverse the green screen and the superposed positive. See Fig. 43o.

Behind the prisms is placed a platinum mirror, which re flects the horizontal image on the vertical image, so that the eye which looks through, say the right prism, sees two colored positives, namely, the red and green and a combin ation of the two colors. The other eye, however, sees only the blue positive, but this, by reason of stereoscopic conver gence, is superposed, as it were, on the other image, so that only one image is ultimately seen, and that in relief and colors. The above diagram will give an idea of the system employed. Essentially the stereochromoscope is a rectangular box of the usual type, carrying on its Lace two prisms forming the oculars. It rests on two supports, being pivoted at P, and held by the button P in the best position for receiving natural or artificial light on the mirrors A B and C D. M is

the platinum mirror referred to, the positives are placed at S s and S and the colored screens at E e, and E' e. The two images at S s in combining give the sensation of one solid image, and, as the images are seen against the colored screens placed at E e and E' e the combination of colors takes place at the sante time. It will be seen by the construction of the stereochromo scope that it allows of the examination of four as well as three positives.* representation of a solid on a plane. A stereoscopic slide.

instrument with two lenses by which an apparent stereoscopic effect can be obtained from a single picture.

STEREO-PHOTO-DUPLICON.—An instrument enabling stereoscopic views to be made with a single lens. The complete instrument, as in Fig. 431, is fitted with a shutter, giving time or instantaneous exposure. The stereoscopic portion of the apparatus is furnished with spectrums manufactured expressly for the purpose, giving absolutely perfect reflections. The principal of their arrangement is shown in Fig. 432, wherein the camera is represented at n, the lense at c, and the spectrum, at A A and s B. The dotted line at E E, indicates the position of the object to be photographed, a view of which is taken from two different points equal to the separation of the eyes, by reflection from the two mirrors A A to the center mirror s x, and from thence through the lens of the cam era to the plate.

It will be seen by reference to Fig. 432, that transposition of the two views is effected; it may be supposed that this reverses the views, but this is not the case, while transposition takes place, both views are taken in their cor rect positive ; thus a negative is produced which may be printed from direct, without the trouble of having to transpose the prints, or cut and remount the negative.

STEREOSCOPE.—If a solid object be viewed from a short dis tance by both eyes on whatever point they are fixed, that point will be seen the most distinctly and other points more or less clearly.

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