KINEMACOLOR A system of producing kinematographic pictures in colour, devised by Charles Urban and G. Albert Smith. Only two colour filters are used, both in taking the negatives and in projecting the positives, but the projected pictures exhibit a remarkable range of intermediate tints, due partly to the fact that the green filter transmits a considerable amount of blue light, the pictures showing blue sky and water, besides black and white, and partly to the laws of persistence of vision relative to colour perception. The camera resembles the ordinary kinematographic camera except that it is built to run at twice the speed, thus taking thirty-two images per second instead of sixteen, and that it is fitted with a rotating colour filter in addition to the ordinary shutter. This filter is an aluminium skeleton wheel A having four segments, two open ones, G and BE, one filled in with red dyed gelatine, B F, and the fourth containing green-dyed gelatine, A B. The machine is so geared that exposures are made alternately through the red gelatine and the green gelatine. The negative is printed from in the ordinary way, when the desired variations of tone become evident in the positive. (See a plate accom panying this work.) It will be understood that there is no colour in the film itself, which, in deed, resembles at first sight any ordinary kinematograph film; the filter is the medium by which the colour is obtained.
The projecting apparatus is shown at B. As in the camera, the mechanism is designed to work apt double ordinary speed, projecting thirty-two images per second, sixteen being projected through the green segment of the colour filter A, and the other sixteen through the red segment. G shows the governing balls communicating with the safety shutter B, compelling the latter to drop out of the path of the lantern rays as soon as the film is passing at a safe speed through the apparatus. The arrow H indicates the direction of the light rays from the illuminant ; c is a light guard, pre venting stray light from passing to the screen ; n the driving pulley, It the film, and B E safety Spool boxes.
A special feature in the formation of the colour filter must now be referred to. Supple mentary to the green filter A B (in illustration A) an overlapping segment of green is filled from C to D with the object of obtaining balance of colour, since red is more vivid to the eye than green. The size of the supplementary segment, C D, is a matter of great importance if perfect results are to be obtained. If it is not large
enough, the yellows will have a greenish hue ; if it is too wide, the green will be too dense and the red will be in excess, giving to the yellow an orange hue. If the red and green filters have been rightly balanced, the revolving disc will transmit to the screen a neutral white " colour." When taking the negative photographs, the speed of film through the camera must be maintained at 2 ft. per second, otherwise the object, when projected, will appear to move at an unnatural pace. Assuming a uniform rate of projection, increased speed of taking will cause an effect of abnormally slow motion in the projected pictures ; while if the subject is taken too slowly, the projected images will show everything moving too fast. In addition to this, the too quick operation of the camera tends to under exposures and excessive vividness of colours, and too slow operating to over exposures and dull results.
Turning now to the operation of the pro jecting machine, it will be understood that at the moment when a particular filter is opposite the optical centre, the monotone image belonging to that colour will be in the gate of the instru ment and be projected upon the screen. The images following in this order at the high speed of thirty-two images per second, the combined effect upon the screen will be a picture reflecting not only red and green, but also their com plementary or accidental colours intermixed with many other hues resultant from the blending of the red and green proper. Although the Kinemacolor system cannot be said to be absolutely perfect, it is the most successful system of colour projection combined with animated effects yet evolved. An ideal process would be that in which the three primary colours of the solar spectrum were embraced, taking the negative images through suitable colour filters and projecting positive images therefrom through yellow, blue and red filters ; but at present the chemical, optical, and mechanical difficulties of doing this in a way that would meet conditions inseparable from kinemato graphy are insurmountable. Not until the three requisite images are taken simultaneously and from a common optical view-point within the time-limit of persistence of vision, and the positives projected under similar conditions, can fully satisfactory results be expected.