Patent GB-199044-A (GB)
Filed: 1923-06-11
Abstract: 199,044. Nolte, C. H. June 10, 1922, [Convention date]. Void [Published under Sect. 91 of the Act]. Colour photography; colour sensitive films; emulsions and sensitive coatings, preparing.- The Specification comprises (1) optical dividing systems for producing three component colour images and arrangements of the partial pictures; (2) arrangements of the sensitized areas on the films; (3) means for obtaining registration in printing from the negative film, or for accurately perforating negative films; (4) the use of screens of less absorbing power than the filters usuallv used in conjunction with a colouring agent for the film; and (5) the preparation of films having sensitiveness of varying degrees within the respective colour zones. (1) The main feature of the dividing system is that the sensitive surfaces receive rays coming from symmetric or concentric parts of, for instance, the objective taking lens. The mirrors may be arranged one behind the other or one within the other. Fig. 1 illustrates one arrangement of mirrors m, p, Figs. 2 , 9, 10 and 11 other arrangements in which the mirrors m, p are of circular or other symmetrical formation. The three images may be arranged side by side on the same film or be in different planes on the same film or on separate films. Supplementary lenses may be used to compensate for the length of path of the central image, and to obtain the same depth of focus as for the other images. In one modification the path of the central beam is lengthened to an equivalent of the other images by a series of reflectors. The central image a, Fig. 7, may be smaller than the outer images b, c and supplementary lenses used to magnify this image to scale for projection. (2) The film may have areas i<1>, k<1>, t<1>, Fig. 17, sensitized for different colours with non-sensitized gaps e<1> or with gaps free from emulsion. The edges of the films may be passed successively through sensitizing baths to obtain the bands i<1>, t<1>, leaving the central band k<1> untreated for the blue negative. The gaps e<1> may alternatively be transverse when the images are in longitudinal sequence. (3) To obtain and maintain register in printing from negatives in which unequal shrinkage may have taken place, two pictures 3, 7, Fig. 18, on the negative 1 may be projected through the positive film 2 and superposed in register on a screen by means of reflectors 5, 6 and the lens 4, the picture 7 having passed through the printing gate. The same projection method may be used to perforate two or more negative films, so that all the positives copied therefrom will be in exact register. (4) The green screen usually used for the red picture by the subtraction method may be replaced by a more transparent yellow or orange screen and the film sensitized with a colouring agent such as pinaflavol. Similarly the usual red screen could be replaced by a transparent screen of different colour when using a corresponding sensitizing colouring agent. (5) To obviate difficulties arising from the fact that coloured shiny surfaces are not faithfully reproduced, or reproduced in tone with other deep colours, the emulsion of the film may be formed of two or more partial emulsions of differently matured grains, or by subsequently treating a completed layer in a bath so that more sensitive zones or points alternate with less sensitive ones.