The history of three-color photography (1925)

Screen-Plates — Historical and Theoretical Data 473 representing the negative and the lower the positive, that is the negative reversed. Fig. 121 shows the effects of correct, under and over-exposure in the positive. A. Forster57 considered that the whites in an Autochrome were not formed by contrast action, but by subjective changes of the silver bromide film caused by exposure. Photometric comparison of the unchanged screen with a white place showed that although the white appeared whiter than the unchanged screen places, yet the latter transmitted more light. By microscopic examination of the whites, there was seen a fine deposit of silver, and this produced the whites of the picture, in comparison to the reddish grey of the unchanged parts. A. Schuller58 thought that Forster's phenomenon could be easily explained from the different power of diffusion of the red, green and blue elements. It was found that the red units were the strongest diffusers, and the green the weakest. It was further determined that this difference disappeared as soon as a strong light diffuser was brought into contact with the film. 1. F.P. 83,061, 1868; Recueil des Brevets d'Invention, 104, ser. XVII, Arts Industries, fasc. 3, 8. Cf. E. J. Wall, Photographic Annual, 1910, 9; Photo-Rev. 1907, 19, 41, 491 ; 1905, 17, 189. H. Snowden Ward, Phot. J. 1900, 40, 142. 2. Le Gers, 1869, March, 11, 15, 20, 25, April, 1, 6. These articles were subsequently published in book form under the title, "Les Couleurs en Photographic Solution du Probleme," Paris, 1869. The passage cited occurs on p. 54 of this book. 3. Special attention is called to this remark, as this principle, the so-called "black condition" has been ascribed to others. 4. "La Triplice photographique et l'lmprimerie," Paris, 1897, 336. Cf. E. J. Wall, Photographic Annual, 1910, 10; A. Mebes, "Die Dreifarbenphotographie mit Farbrasterplatten," Bunzlau, 1911, 10. 5. Phot. J. 1910, 50, 197; Phot. Coul. 1910, 5, 171; Brit. J. Phot. 1910, 57, Col. Phot. Supp. 4, 45, 52, 62, 68; abst. ibid. 1917, 11, 24. 6. Phot. Ind. 1911, 929, 956, 998; Jahrbuch, 1912, 26, 272. 7. J. Soc. Arts, 1908, 56, 195 ; Brit. J. Phot. 1908, 55, 41 ; Col. Phot. Supp. 2, 12; abst. Brit. J. Almanac, 1909, 638. 8. "On some experimental methods employed in the examination of screenplates," Phot. J. 1910, 50, 197; Brit. J. Phot. 1911, 58, Col. Phot. Supp. 5, 45, 52, 62, 68; abst. Brit. J. Almanac, 1911, 613; Jahrbuch, 1911, 25, 223. 9. "The Scientific Requirements of Colour Photography," London, 1897, 6; abst. Brit. J. Phot. 1897, 44, Supp. 6. 10. Brit. J. Phot. 1895, 42, 774. F. E. Ives, Amer. Annual Phot. 1895, 24 commenting on Joly's statement said that Konig's curves are compressed at the violet end and are misleading. As a matter of fact, the curves given by Joly, were drawn on the diffraction spectrum scale, and therefore would actually give correct curves in accordance with the wave-lengths, and would not be compressed. Obviously Ives was ignorant of the diffraction spectrum. He also said : "Now, however, comes the suggestion from one who is no less than a F. R. S., that, since Konig's curves are more nearly 'correct' than Maxwell's, with which the writer succeeded, therefore, there is great latitude in the selection of color screens for this work. The inference is that as good, or better results should be obtained with screens proved according to Konig's curves .... Konig's curves do not represent mixtures of three spectral colors, but mixtures of red and violet, with a fundamental sensation which nothing in the spectrum represents, and which, therefore, cannot be optically mixed with other colors, as required in composite heliochromy." 11. Phot. Mitt. 1898, 35, 273; 1899, 36, 8, 14, 35, 46, 65. 12. Mees, loc. cit. 199. 13. "The Luminous Equivalent of Radiation," taken from O. Steindler, Wien. Sitzber. 1906, 115, II a. Cf. P. G. Nutting, "Outlines of Applied Optics," Philadelphia, 1912, 129, 141.