GB515932A - Improvements in processes for printing multicolour photographic and kinematograph images - Google Patents

Abstract

515,932. Colour photography. GASPAR, B. March 14, 1938, No. 7828. [Classes 98 (i) and 98 (ii)] A photographic printing apparatus comprises a light source composed of differently coloured lights, a gate for the film to be printed and a gate for the light-sensitive film, the latter gate being in the path of light transmitted by the former gate, a photoelectric cell selectively sensitive for a component colour of the composite printing light or arranged behind a filter-selectively transmitting that component, the photoelectric cell being exposed to a part only of the light transmitted by the film to be copied outside the picture area and connected to a variableopacity device arranged between the light source and the lightsensitive film. As shown, the apparatus comprises three light sources 1, 2 and 3 and three colour filters 4, 5, and 6, two semitransparent mirrors 7 and 8 and three lens systems 9, 10 and 11. The composite beam of light 12 is reflected by the mirror 14 to print the three-colour original 13 on to the light-sensitive film 15 by means of the lens system 16. A mirror 17 reflects the light passing through an aperture outside the picture area in the film gate carrying the original film 13 to a beam-splitting device 18, 19 to give three beams passed through colour filters 20, 21 and 22 to three photo-electric cells 23, 24 and 25 polarized by batteries 26, 27 and 28. The potential differences between the ends of the load resistances 29, 30 and 31 control the currents in the anode circuits of the valves 35, 36 and 37 and thereby control the electromagnetic devices 38, 39 and 40 that open or shut the diaphragms 41, 42 and 43 in the lens systems 9, 10 and 11. A second mirror may be arranged to reflect light to a separate photo-electric cell controlling a diaphragm between the two films to control the total printing light intensity. The spectral composition of a composite light beam may be altered by apparatus comprising fixed yellow, magenta and blue - green wedges co-operating respectively similar movable wedges controlled by solenoids influenced by variations in the light transmitted by the original. The wedges may be arranged between the original and the light source or between the original and the printing film. A part only of the colour selection pictures may 'be printed at one time, or different printing lights may print different and successive component images at successive gates. Portions of the original not required for the image may be exposed completely prior to development and these portions used for the scanning. Light acting on one layer only may be used. The colours may be produced by dye-destruction, colour development or dyetoning. The apparatus may be applied in connection with cinematograph or ordinary films or in the production of paper prints.