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Historical and Theoretical Data 7
This would seem an appropriate place to introduce a note relating to a publication by G. Fritsch, of Berlin.13 He says : "In the text of a diary of a journey, which is exhibited in document, there will be found under the title: 'On Color Photography' the following article, from which extraneous matter has been omitted : 'That which we see in nature as an innumerable number of color tones is composed of a few fundamental colors, which by their common action produce the multiplicity. One may trace these colors, even with not absolute accuracy, as is well known to three, for which colors blue, red and yellow have been assumed as a color triangle, in the middle of which should lie white. This is now, as Helmholtz has shown, not actually the case ; the colors do not lie in a triangle, nor in a circle as Newton assumed, but on a curve, and white in the focus of the same. Blue and yellow give no spectral green, and Helmholtz found three other colors that better fitted the requirements, namely a deep red, green and violet, which, however, produce no spectral yellow. If the previously mentioned three colors do not now quite correspond to the natural colors, yet their action is so approximate that we may start from these as a basis. If we illuminate an object with pure yellow light, or if we allow the rays proceeding from it to pass through yellow glass, we obtain an image, in which all tones that contain yellow, appear more or less bright, all the others, however, black. If we illuminate the same object with red light, we obtain red lights, the others are also black ; with blue illumination blue and black. In this way I am in a position to separate the fundamental colors and to register an image of each of the same. I obtain in this way then in the collodion film, the places of the bromo-iodide of silver film decomposed by the colored light whilst all the rest appears as shadows and, therefore, transparent. This film, which can be stripped, has first of all the characteristic bluish-grey color of the decomposed bromo-iodized silver, it can, however, be colored in different ways by the action of different salts. . . . For color photography the aim should be so directed that instead of a middle tone, actually the extreme colors should be obtained in as great a purity as possible, which is certainly possible to a much higher degree than now appears to be the case, and one would then be in a position by the aid of this method to obtain three different pictures, in which the yellow lights would appear yellowish, the red lights reddish, and the blue lights bluish. If now I take an object in the ordinary way and so intensify the negative, that in the positive all the lights appear white and only the shadows can be distinctly differentiated, so that the positive, as the photographer says, appears snowed up (chalky). I could transfer the colored collodion films on to the same and thus bring the local tones into the picture ; the respective covering of the colors would produce the middle tones."
This note was written in South Africa and was dated Oct. 10, 1863. Fritsch stated that he was not aware of Maxwell's work, and was