GB451699A - Process of colour photography - Google Patents

Abstract

451,699. Colour photography. MANNES, L. D., and GODOWSKY, L., Kodak Park, Rochester, New York, U.S.A. Nov. 10, 1934, No. 32445. [Class 98 (ii)] A photographic emulsion layer comprising a mixture of differently colour-sensitized grains is exposed to an object in colours, developed in an ordinary developer without fixing, re-exposed to uniform light of a colour which affects only one set of grains, and colourdeveloped to the minus colour, these exposure and developing steps being repeated for the remaining set or sets of grains, and the silver images produced by the developments being finally dissolved out as by Farmer's Reducer, leaving a multicolour image of dyed gelatin. In a two-colour process, a mixed emulsion layer of normal thickness is used, containing grains sensitized to orange-red as by pinacyanol or naphthocyanol, and grains sensitized to green as by pinaflavol. To reduce the effect of blue-violet rays, the layer is either exposed to the coloured object through a yellow filter, or the orange-red sensitive part of the emulsion is rendered less sensitive to blue-violet as by immersion in a bath of Indian Yellow, which may also contain silver nitrate. To preserve the balance of the two parts of the mixed emulsion, the blue-green sensitive part may also be treated with a silver nitrate bath. After exposure, the layer is developed to completion, preferably with a soft developer such as metol, glycin, or acid amidol, containing as little sodium carbonate as possible to produce minimum relief. Caustic alkalies in the developer are avoided. The layer is then exposed to uniform light and treated with a colour-forming developer yielding a blue-green image, such as one containing dimethyl-paraphenylenediamine hydrochloride with alpha-naphthol or indoxyl, or paraphenylenediamine hydrochloride with trichlornaphthol. After washing, the layer is exposed to uniform white or blue-green light and treated with a colour - forming developer yielding an orange-red image, such as one containing thioindoxyl or para-nitrobenzyl cyanide with dimethyl-paraphenylenediamine. The layer is washed and finally treated as with Farmer's Reducer to remove the developed silver images. A similar three-colour process is referred to in which a blue-green component is developed as above, and the other components are developed with a colour-forming developer containing diethyl paraphenylenediamine hydrochloride to which is added bromo-thio-indoxyl for the magenta component and benzoyl acetone for the green. U.S.A. Specifications 1,897,866 and 1,900,870 are referred to.