Patent GB-756075-A (GB)
Abstract: 756,075. Photographic processes. CIBA Ltd. Dec. 22, 1953 [Dec. 23, 1952], No. 35620/53. Class 98 (2). Photographic colour or stereoscopic records of the " variable area " type are produced on films having cylindrical lenticulations by using a primary light distribution which gives strips extending longitudinally of the axes of the lenticulations the intensity of the strips varying from a maximum at the edges to a minimum in the middle and using a line screen approximately in the plane of the film with the lines transverse to the axes of the lenticulations, the film being developed to a high gamma. The variation in the primary distribution of the light is achieved by means of the diaphragms shown in Figs. 2 and 3 or by means of the variable density wedge shown in Fig. 4. For the production of a colour record three diaphragms G, R, B (Fig. 1) are used and the separation negatives are exposed in turn using the appropriate diaphragm to give the three colour records B<SP>1</SP>, R<SP>1</SP>, G<SP>1</SP> in the lenticular film. The diaphragms are in the same plane AA<SP>1</SP> as the colour filters used to project the completed record. The negatives may be copied on to the film by projection or by contact. The line screen may be on a separate film laid on top of the lenticular film or it may be produced on the lenticular film itself (e.g. by producing lines of reduced sensitivity, by tanning, on the sensitive layer of the film). In the case of contact printing the screen may be produced on the negative itself. The line screen may be one in which the individual lines have a continuous density variation in a direction transverse to the lines. For reproducing stereoscopic colour pictures the three record zones B<SP>1</SP>, R<SP>1</SP>, G<SP>1</SP> are each divided in half, one half for the left-eye image and the other half for the right-eye image. Six negatives are necessary, the three right-eye images being exposed through a polarizing filter with one half of each diaphragm covered up and then the three left-eye images are exposed through a filter with its plane of polarization at right angles to the first and the other half of the diaphragms are covered up. In an example the lenticular film is sensitized with an aqueous solution of ferric ammonium citrate, silver nitrate and citric acid. A separate line screen is made on a film sensitized as above, exposed through a lenticular film and a slotted diaphragm and physically developed in an aqueous solution containing metal, tartaric acid and silver nitrate. The three separation negatives are prepared on a film sensitized and physically developed as described above. After exposure according to the invention, the lenticular film is physically developed in the above developer to y = 10. It is then hardened and fixed and toned by treatment in a bath comprising an aqueous solution of gold chloride, borax and sodium acetate followed by a bath comprising an aqueous solution of potassium platinochloride and phosphoric acid. Finally it is immersed in a bath comprising an aqueous solution of sodium hydrosulphite and sodium carbonate. A process is described for the production of colour record negatives consisting of dyestuff images by copying the ordinary negatives on to positive film, developing with metol/hydroquinone, fixing, dyeing in a bath containing N- [p - (p - hydroxy - m - carboxyphenylazo)phenyl]- N<SP>1</SP> - [p - - (m sulphophenylazo) - o - methoxyphenyl]urea (sodium salt), treating in a precipitating bath containing 2-naphthyl-biguanide hydrochloride, bleaching in a dye bleach bath containing sodium chloride, potassium bromide, hydrochloric acid and 2-amino-3-hydroxyphenazine hydrochloride followed by a silver bleach of sodium chloride, copper sulphate and hydrochloric acid and fixing. Specifications 701,529 and 704,415 are referred to.