. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. A NOTABLE ADVANCE IN COLOR PHOTOGRAPHY. 525 of an old theory by ruling glass screens with infinite fineness and accu- racy and in breaking up the original negative into three, from which plates can be made to print on ordinary paper. All makes of ruled polychrome screens can be used to obtain the nec- essary negatives for the Sampolo-Brasseur process. The best are those ruled in lines in groups of threes, one line being in a reddish orange
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. A NOTABLE ADVANCE IN COLOR PHOTOGRAPHY. 525 of an old theory by ruling glass screens with infinite fineness and accu- racy and in breaking up the original negative into three, from which plates can be made to print on ordinary paper. All makes of ruled polychrome screens can be used to obtain the nec- essary negatives for the Sampolo-Brasseur process. The best are those ruled in lines in groups of threes, one line being in a reddish orange color, one in a yellowish green, and the other in a blue-violet color. These colors may vary somewhat, as the dry plates of different makers are not equally sensitive to the various colors of the spectrum. In case of a serious departure from these colors, corresponding changes nnist be made in the printing inks used. The screens made by Mr. Brasseur have 581 lines per inch, with no mistakes in any inch of more than one fifty-thousandth of that space. Having obtained the necessary negative, a positive on glass is W//M//^^M/MMm///ffMmP77m '^/////M///////M///////////////M7Z77, ^: Wm/^///////////M/////////////y7P777. m/^//mM//MWM/yy//////w/?7/, W/////////''////////////////////////7P7^A w////y/////////y///////M///M//7P:^?;^, '//y/M/M////M/////////////////;!7ZW, V////////////////////////////////////,77;7?. J Fig. 3.—Black and white screen placed over positive and show- ing only one of the pos- itives. Fig. 4.—First step in making negative. Only one-third of the plate is covered, and prints from this could not be properly superposed. Fig. 5.—Completed neg- ative of one of the im- ages. Entire surface is now occupied by image which on original only occupied one-third. This positive is apparently no different from ordinary positives, but if it ])e examined under a microscope it Avill be found to consist of three interwoven images, corresponding with the three sets of lines
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Keywords: ., bookauthorsmithsonianinstitutio, bookcentury1800, bookdecade1840
