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Report of Progress Committee 1925-26 9
A practical disadvantage of the lenticular film system hitherto has been the necessity for employing a projector lens of the same focal length as that used in the camera. By a recent improvement^" the lenticular elements are arranged so that the pupil of emergence is at infinity or at a great distance in front of the sensitive surface of the photographic film or plate. By this construction the images of the color selecting filters used in the objectives are independent of the focal lengths of the objectives used in taking or projecting.
Another British patent^^ covers a process in which multi-color negative or positive images of separately tinted color record negative images are produced on a film having one surface covered with minute lenticular elements in apparatus employing an annular diaphragm having an opaque central portion which covers the useful lenticulated surface, and a transparent annular portion which covers the inoperative neighboring area.
Thornton Three-Color photography /^ which is the making of a 3-color motion picture film by the use of an apparatus with a single lens and beam splitting device and a film of double width, is described in an abstract of British Patent 238,688. One part of the film is prepared with a 2-color screen mosaic of green and violet which reproduces in the negative the magenta red and the yellow portions of the subject. The second portion of the film receives the light through an orange-red filter incorporated in the surface of the film, thus producing a full tone negative image of the blue-green portion of the subject. In making the film the color layers are coated first, then a thin substratum, and on this the panchromatic emulsion. Exposure is made through the support and color screen layers. The positive film is similarly prepared, although red, blue and yellow may be used instead of the colors employed in the negative film.
Another method of color photography^^ has been proposed in which the color is produced after development by the oxidation of leuco-dye bases with which the silver halide grains have been respectively treated. Each third of a silver bromide emulsion would be separately sensitized to one part of the spectrum, with a subsequent attachment to each of the leuco-bases of a dye of the complementary color. Complete success has not yet been achieved.
10 British Patent 247,168— To The Soc Mondiale du Film en Couleurs, Keller-Dorian.
" British Patent 245,118— To The Soc. Mondiale du Film en Couleurs. 12 "Brit. J. Photo," Color Sup., 20, Feb. 5, 1926, p. 8. " "Phot. Ind.," 23, Dec. 7, 1925, p. 1330.