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CHAPTER III STILL CAMERAS AND CHROMOSCOPES
In the main this chapter is devoted to cameras and chromoscopes1 (p. 145) in which one or more plates or films are used to receive the color records. But there must obviously be some overlapping with those sections that deal with allied subjects, such as the optical data and cinematography in colors. No hard and fast line can be drawn, as some of the designs may be used for motion picture work.
Cros and du Hauron. — As in so many other branches of color photography we find that Cros and du Hauron anticipated all subsequent workers. The latter, as pointed out elsewhere, sent a paper to M. Lelut, in 1862, with a request that it be read before the Academie des Sciences, and that this paper was rejected. It was reprinted in 18972 and du Hauron described a photochromoscope with figure, here reproduced, Fig. 18. It is unnecessary to enter into the construction, suffice it to say, that the three mirrors, shown in continuous lines, are at right angles to one another, and the paths of the rays from the transparencies are shown by the broken lines, as is also the position of the composite image on the extreme right; R, R, R, representing the adjustable mirrors for illuminating the pictures.
Du Hauron suggested that it would be possible to modify the results by varying the color of any positive, locally or entirely. Also that the instrument could be used for stereoscopic transparencies, by merely doubling the length of the apertures. Further, he says, it is possible to use only three single positives, with 'less perfection it is true," by arranging for the one eye to see the red and yellow proofs, and the other eye to see the blue ; a method, which is physiologically unsound, but which has been subsequently patented by others.
Again in 1869, du Hauron said :3 "Si Ton projette les images de ces trois epreuves sur une surface blanche au moyen des trois lentilles, placees de telle sorte que les trois images se superposent exactment, on voit apparaitre sur l'ecran une image polychrome, qui est le representation fidele de la nature. Pour confondre les trois epreuves en une seul tableau, on peut remplacer l'appareil polyoramiques a trois lentilles par un compose de trois glaces sans tain, situees les unes derriere les autres par rapport a l'oeil du spectateur, auquel elles envoient chacune par reflexion une epreuve differente. Pour eviter que l'image de chaque epreuve se dedouble par sa reflexion sur deux faces paralleles de la glace correspondente, il est necessaire de disposer entre l'epreuve et la glace une lentille convergente, ou verre d'optique, dont le grossissement aura pour effet de placer l'epreuve a une distance telle que ce dedoublement devienne insensible."
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