GB190625908A - Improved Mirrorbox for Photography in Colours. - Google Patents

Abstract

25,908. Pfenninger, 0. Nov. 16. Photochromoscopes.-In photochromoscopic apparatus such as is described in Specification No. 3784, A.D. 1895, methods are described for compensating for the unequal contraction of the three component pictures which results from the passage of light through the inclined reflectors for the component images, and which materially affects the superposition of component prints in three-colour printing. In the mirror box shown in Fig. 2, no objective lens is used in the front aperture, three lenses o<1>, o<2>, o<3> being provided for the component images. In one method of compensation, plates P<3>, P<4>, P<5> similar to the reflecting-plate P' are interposed in the side compartments, so that each beam forming a component image is transmitted through two of these plates. An additional plate or lens Z may also be required in the central path to compensate for the shorter path of the central beam. If it is desired to correct for the contracted images so as to bring the shape more nearly to correspond with its normal shape, three or other additional plates must be used in the compartments, but sloping from front to back in the same manner as described in Specification No. 25,907, A.D. 1906. In another method, prismatic reflectors P, Fig. 5, of small angle, are used. If two such reflectors are used, the plates P<3>, P' shown are not necessary. Reflecting-prisms may be used instead of reflectors m. The reflectors P need not be used at forty-five degrees, but smaller angles can be employed as shown in Fig. 6. The prisms in such cases are not right-angled, but greater or less as the case may be. Specifications No. 3784, A.D. 1895, No. 23,940, A.D. 1898, Nos. 13,666, 15,753, and 17,514, A.D. 1899, Nos. 10,795 and 12,181, A.D. 1900, No. 13,468, A.D. 1902, Nos. 3729 and 24,829, A.D. 1903, and Nos. 322 and 14,623, A.D. 1905, [Abridgment Class Photography], are referred to.