Patent GB-394987-A (GB)
Title: Improvements in or relating to colour cinematography
IPC: G03B33/00
Filed: 1932-01-05
Abstract: 394,987. Colour kinematography. FINLAY, C. L., 62, St. Albans Road, Watford, Hertfordshire. Jan. 5, 1932, No. 335. [Classes 97 (i) and 98 (ii).] A method for producing a film having a regular colour pattern screen in accurate positional relationship to the perforations consists in forming temporary perforations in the film stock by which it is traversed during each successive colour-printing operation in exact register with the printing element, and thereafter forming the permanent driving perforations whilst the colour markings are maintained in visual register with a master stop-out screen in fixed positional relationship to the perforator. Alternative modes of procedure are described. A screen film for making a positive by contact printing from a negative is produced by the same process as is used for making the screen as the negative, the direction of the rulings or arrangements of the colour markings being correspondingly modified for the necessary pattern registration. The registration itself is accurately effected by the tractor perforations during printing. For the production of the multi-colour screen film a wide film stock, Fig. 5, which can -be subsequently cut up, may be used and provided with temporary perforations 16 outside the marginal width 20 of the standard film, the final tractor perforations being made along the tracks 19. To provide for a sound track a track 18 can be left uncoloured at the side of the picture areas 17. The different colours of the screen pattern (e.g. 43, 44, 47, Fig. 9), may be produced either by mechanical printing (e.g. a plate or roller) or by a photographic process. For the mechanical printing method, the temporary perforations 16 are used to drive the film and register the colour printings. In a photographic process two colours may be produced by means of printing films having thereon black and white screen patterns (e.g. Figs. 6 and 7) in accurate positional relationship to perforations in the film, which perforations register with the temporary perforations 16 of the film stock of Fig. 5. The two line-work patterns of Figs. 6 and 7 when superposed constitute the master stop-out screen of Fig. 8, which is used for visual registration during the subsequent production of tractor perforations along the tracks 19, Fig. 5. Alternative methods of producing the printing films are (1) to print from a screen plate 10, Fig. 1, having a negative pattern of Fig. 6, on to a sensitized film 11, stepping. and registering the film during printing by a feed and registering block 15 : (2) to print from a screen plate bearing the actual design of Fig. 6, by the above method (1) on to a film, and to print from this film on to another similarly perforated film ; or (3) to print from a screen plate on to unperforated film and subsequently perforate the film, using the screen plate to register the perforations with the printings on the film. Having obtained the films of Figs. 6 and 7, they are used to produce the colour pattern on the film stock of Fig. 5 by successive steps which are described with reference to diagrammatic drawings of apparatus, Figs. 3 and 4 (not shown), specific formulae for sensitizing, dye, and treating baths being given. The steps are as follows : colouring the base with a dye (e.g. blue violet) : forming the temporary perforations 16 by the same machine as is used for the printing films : producing a bichromate or silver dye resist image of one of the printing films (e.g. Fig. 6), using the perforations 16 and those in the printing film to register the printings : bleaching the exposed areas not covered by the resist image ; dyeing these areas with a second colour (e.g. red) : resensitizing and producing a second resist image from the second printing film, Fig. 7: bleaching the exposed areas and re-dyeing these with a third colour (e.g. green). This produces the pattern screen of Fig. 9 having blue violet lines 43 and red and green areas 44, 47. The colour pattern outside the margins 20 are then used in conjunction with the master stop-out screen of Fig. 8, situated in positional register with the perforator to register the final tractor perforations along the tracks 19 with the screen pattern. The film is subsequently cut along the standard width lines 20 and the margins containing the temporary perforations are discarded.