COLOUR PHOTOGRAPHY.

New Zealand Graphic, Volume XVII, Issue I, 4 July 1896, Page 27

COLOUR PHOTOGRAPHY.

Scientific London is now deeply interested over the latest discovery in colour photography. by Professor Gabriel Lippmann, member de I’lnstitut de France and professor of natnral science at the Sorbonne. Professor Lippmann recently explained his discovery at the Royal Institution, before a most distinguished scientific audience, which included among others, Lord Kelvin, Sir G. Stokes, Sir Frederick Abel, Sir James Chrichton Browne, Sir Benjamin Baker, Professor Dewar, Dr. Frankland, and many others. A number of coloured photographs, embracing figures, flowers and landscape were exhibited by aid of the magic lantern and created such a sensation that loud applause followed as the brilliant colours were thrown on the screen, a most nnusual feature in a lecture at the Royal Institution. 1 called on the Professor and subjoin the following information from his own lips, which has not yet been made public. As a practical man the Professor evidently realized that seeing is believing, and therefore began operations by showing me the very plates he had used for illustrations at his recent lecture. There, sure enough, when viewed at the proper angle, I beheld the dream of photographers for the last fifty years realized—photos, coloured by natural process. A strange sensation this the first glimpse of a fresh secret wrung from the unknown recesses of nature—a sensation, indeed, fraught with reverence. ■ You will observe that the colours shown on the plate are not due to coloured substances, not to pigments. They are of the same nature as those of the soap bubble, so called interferential colours. Note bow they change when you hold them up to the light,' and the picture before me, as I held it up, underwent all the changes of the rainbow. , .... The Professor proceeded to explain that in order to obtain coloured photographs by his method it was first necessary to have a transparent, grainless photographic film, capable of giving a colourless fixed image by the usual means. The preparation of such a film had been the most difficult part of his work, for, once this attained, the second necessary condition once hit upon was easily carried out, namely the employment of a metallic mirror placed in immediate contact with the film during the time of exposure. This mirror was formed by means of mercury, the plate being first enclosed in a camera slide, with the film side, contrary to the method usually employed, turned against the back wall of the camera—thus not in direct contact with the object. Mercury was allowed to flow in behind it from a small reservoir connected with the elide by India rubber tubing, thus forming a layer of mercury right over the surface of the plate. After exposure the mercury flows back into the reservoir, which is lowered for the purpose. The plate is developed in the usual way, and, when dry, the colours are seen by reflection. The scientific process Professor Lippmann further explained thus:— * During exposure in the camera, the light irom the lens is reflected back on the film by the mercury mirror. In consequence of this, the luminous vibrations from stationary waves, which imprint their forms (id est, colours) upon the sensitive fi'm. The particular colour of rays of light is known to depend upon the particular form or length of the light waves. Without the mirror these waves, travelling through the camera at the rate of 186.000 English miles per second, would leave no record on the plate as to their wave length. * That is to say, they would leave no record of the colour which they might produce to the human eye.’ And here M. Lippmann remarked that there is some analogy between his invention and that of the phonograph. In the phonograph the sound vibrations are imprinted in the wax of a cylinder and are reproduced afterward. In his invention the vibrations are made to imprint their form in the body of the photographic film, and this film, when viewed by aid of white light, reflects precisely the colours which it has received on its surface. The exposure necessary to produce this effect is one to two minutes in sunlight and ten to fifteen minutes in the shade. The colours are as minutely reproduced as the monochrome effects of photography, the Professor assured me. This is evident when they are projected on a screen—as minute and distinct as a Holbein picture. I ventured to ask whether he has yet succeeded in reproducing or in multiplying on paper the coloured photographs he had shown me. ‘Not yet,’ he replied. ‘That is the problem lam now occupied with. I have not yet reached the paper printing stage. At present I have attained what I would venture to call the stage of the daguerrotype in colours. For, as you know, at first Daguerre was not able to multiply his photos. But I now feel certain that the transference of coloured photographs is theoretically possible, whether I may be the first to succeed or somebody else.’

* But surely, monsieur,* I put in, * there is an enormous fortune for the one who

first carries this beautiful idea into practice. It seems almost a pity for you to come over here and tell all you know, perhaps. for the benefit of others.’ * Well, you see. Lord Kelvin asked me to come to London. Besides, being a professor at the Sorbonne, I am not supposed to work for anything else but the advancement of science. Money making is not part of our programme. I came upon this idea in my laboratory at the Sorbonne, after the subject had been in my mind over fifteen years. Those transparent films have given me a lot of trouble.’