Patent GB-547216-A (GB)
Title: Improvements in making photographic silhouette records
IPC: G03C7/25
Filed: 1940-10-24
Abstract: 547,216. Composite colour photographs. TECHNICOLOR MOTION PICTURE CORPORATION. Oct. 24, 1940, No. 15642. Convention date, Jan. 16. [Class 98 (ii)] A silhouette mask for use in combining, by dye imbibition printing, separatelytaken colour value records of a composite scene, e.g. records of foreground and background components, is made by producing a latent image of a component scene in an unflashed emulsion layer which is so sensitized and dyed that its density range corresponds to an exposure range which is a comparatively short intermediate section of the exposure range of said component scene record, developing the latent image, removing the gelatin which received an exposure below the said intermediate section, and rendering the remainder substantially opaque for the light to be used for printing with the mask, e.g. by dyeing it, so that there results a light-absorbing record whose density is very high on one side and very low on the other side of the said intermediate range. An emulsion layer may be used for the printing, which is sensitive to two spectral exposure-light ranges but absorbs less light of one range than of the other. In the method described, a foreground object illuminated with white light and having a plain backing which is coloured and illuminated with minus-blue light, is photographed to produce blue and green colour component negatives. The illumination is such that the intensity of the green reflection from the backing is at no point less, and is preferably at all points greater, than that from any point of the foreground. There results a blue record negative Fb with transparent backing area, and a green record negative Fg with opaque backing area the foreground image in which at no point has a greater density than that of its backing area. From negative Fb a positive Pb is made, and thereafter negative Fg and positive Pb are printed in turn, avoiding pre-exposure or flashing, with light including the range from blue to yellow, on to a film which is colour-sensitized as with erythrosine to blue, blue-green, green, and yellow, and is dyed with a mixture of Tartrazine, Rose Bengal, and Acid Magenta so that its absorption decreases from blue to yellow. In such printing, the blue, green, and yellow components of the printing light penetrate the emulsion layer to different depths, and on developing, a silhouette mask is produced. The developing is performed with a tanning pyro developer, and the image is bleached to silver ferrocyanide in a ferricyanide bath which produces still further hardening at the developed areas. The unhardened gelatin is removed with hot water, and the resulting relief is dyed as with Brilliant Paper Yellow Concentrated. The opacity of the relief may be increased by redeveloping the silver ferrocyanide image to silver, and, if desired, converting this to silver sulphide. It constitutes a background mask having substantially opaque foreground areas and clear celluloid backing areas. From this mask a complementary foreground mask may be printed, if desired by employing similar sensitive material and method of processing. These two masks are, according to the embodiment described, used in producing a set of colour-record composite relief matrices from two sets of colour-record negatives, respectively of the foreground and background components of the scene, and these are dyed up and used to produce the composite colour picture by imbibition printing. Reference has been directed by the Comptroller to Specification 538,628.