The age-herald., 1897-10-01
COLOR IN A PHOTOGRAPH.
Prof. John jOly, of TrintOn College, Dublin,
 Ireland, is the Inventor.
From the Chicago News

From the Chicago News
 "The latest word in photography" at this time has to dc with the making of pictures in such way that the light by which they are viewed shall bring out the natural colors.
 To make celo-ed pictures with the camera has been the dream of the men who manipulate that instrument ever since the first camera was put into ser vice. Over and over again it has been declared by scientists who ought to know that the hoped for invention could never materiaLize; yet enthusiasts have not been lacking to burn the midnight oil in order to prove the scientists wrong. And at last it appears that the longed for invention has been acomplished- that photographs actually showing the colors of the thing photographed not only can be made, but are actually be- ing made.
 Prof. John Jolly, of Trinity college, Dublin, Ireland, is the lucky, inventor. It should be understood at the start, however, that his photographs are not made on paper and that the color effect is not produced by chemically changing the surface of the photograph so that different parts will reflect different shades and colors to the eye. Joly's photographs are made on glass, and, viewed by themselves, show only neu- tral tfnts, somewhat similar to those we are accustomed to see in photographs printed on paper. It Is only when the light passes simultaneously through them and a properly prepared medium of transmission that the color effect is produced
 The Joly photographs, however, may be made by amy camera in which glass platss' and not films ar5 employed and their making requires no more skill than 1s possessed by any amateur, and no ap- paratus d.fferdng from that used in mar- ing ordinary photographs is necessary, beyond two simple looking plates of glass, one known as the 'atalking screen, and the c'thsr as the viewing screen"
 Each is covered on one side with a thin film of gelatine, and this is ruled with transparent, colored inks, Tn lines so thin that 1t takes 400 of them to cover the space of an inch. These lines an'@ arranged in thress on both screens, the number three corresponding to the pri- mary colorss of nature. On the "tak- ing screen" the colors are reddish-or- ange yellowish- green and blue-violet; on the "vlewing soreen' the colors are red, green and violet.
 When photograph is to be obtained by the Joly method the sensitive plabe> to be exposed is put into the pia.e holder in the ordinary manner the hold CT being so modified that a second thin glass plate-the taking screen"-nfay be inserted at the same time, In such a way that the light must pass through the screen before it falls upon the, plate. In it's passage through the screen cer- tain notifications of the light must necessarily take place. According to MT. Joly's theory, rays corresponding 10 the reddish-orangA, and these only, pass unilapeded through the lines of that color; rays corresponding to the yellow fsln-green only through lines correspond ing to it; and violet-blue rays only, through the lines which they match. Rays from surfaces tinted or shad d with composites of the three primary colors must, of course, pass through all three lines, though not so freely and sn proportions corresponding exactly to the composite shades. Rays from sur faces showing tints composed Of the two primary colors pass through only two of the lines, and in the proper pro- portioat. The result is a. negative, show sng ndt colors, indeed, but what Prof Joly terms "color valus@."
 When such a negative has been ob- tadned, a. positive is printed on a giass, s,, exactly as positive would be printed on paper, from aU ordinary negative. Of course, as many postives as desired c'n be made from each negative To pr ng out the colors corresponding to the "col- ol. values the "vleWing screen Is fl Jted ;lo the positive so that the light vii shine through both. When this is done beautiful transparent picture IS pro duced, wherein the colorS of the obJect photogra phed are shown with Starhhng Ibrilliamce and close fidelity to nature.
 Prof. Jo1y began the exp srimen.s which led to the discovery of this method of photographIlcally showing cobors some seven or eight years ago, when he was asked to prepare a paper on colors in photography. Naturally, he took advant- age of all that had been done before by rhoaa working along similar lines. The friple-nagat triple-ls ntern scheme of E. J. Ives, of Phalade1phia, the work of Clerk Maxwell Ducos-Dlhaurain, Col elm and of mfany others was laid under contribution, and much benefit was de- qived therefrom. Prof. Jolly was. how ever, obliged 10 make long and patient investigations to "tight wave lengths" |" "color curves in the spectrum and a whole lot of obscure optical phennmena, the recital of which would be interes ing only to those who have taken up the study of ligh. and color in an ultra scientific way.
 Ait the same time, it should be under stood that while he makes use of some of the same principlas employed by every scientific seeker for colons in phdtog- raphy, his final methods and results are entirely his own, his pictures differing radically from the "color selective' pho tographs of Chassagne and the frides- cant color photographs of an earlier French scientist. Although the Jody pictures are the first to be placed pHec- tically before the photographic world credit for his discovery is disputed by charles McDonough, of Chicago, who has somewhat similar process for pro- ducing the same results and who has begun an "interference' suit, claiming priority of invention. Just how the courts will decide the suit it is of course impossible to foreshadow at this writ ing.
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