GB805891A - Process and apparatus for producing photographic colour prints - Google Patents

Abstract

805,891. Photo-electric exposure control. AGFA CAMERA-WERK A.G. April 14, 1955 [April 21, 1954], No. 10833/55. Class 40 (3). [Also in Group XX] In apparatus for producing a photographic colour print from a colour transparency three exposures are made simultaneously or sequentially with three primary colours, the quantity of each colour impinging on the lightsensitive material being measured photo - electrically to interrupt the supply of light of that particular colour. As shown (Fig. 1), three colours, blue, green and red, are separated by filters 5, 6 and 7 from white light produced by sources 2, 3 and 4. The three colours are reflected on to an opal or ground glass screen 9 located in the focal plane of a condenser 10 and directed through negative 12 on to the sensitive surface 15. A half-silvered mirror 14 between the negative and the sensitive surface diverts part of the light which has traversed the negative to further half-silvered mirrors 19 and 23. Mirrors 19 and 23 divide the light reflected by mirror 14 into the three equal parts, one of which falls on each of cells 16, 17, 18 sensitized respectively to the three primary colours by filters 20, 24, 25. Each cell controls the charging of a condenser which, through a pentode amplifying circuit, switches off the appropriate lamp when the quantity of the particular colour is adequate. If the exposure of each colour is to differ the condenser charging potentials may differ. In the arrangement of Fig. 2 (not shown) a rotating disc has mounted in it three filters which are successively interposed in a beam of light from a lamp, a photo-cell responds to the light which has traversed the negative and rotates the filter to terminate the exposure of a particular colour and commence that of the next.