Patent GB-630853-A (GB)
Title: Method and apparatus for printing color photographs
IPC: G03B27/73
Filed: 1946-04-26
Abstract: 630,853. Comparing colours; printing colour photographs. GENERAL ANILINE & FILM CORPORATION. April 26, 1946, No. 12691. Convention date, June 12, 1945. [Classes 97 (i) and 98 (ii)] A method of printing a photographic integral multilayer colour positive from a photographic integral multilayer colour negative includes the steps of comparing a grey control patch formed by developing and fixing a portion of the negative material which has been exposed to white light with a standard grey on similar negative material, whose printing relation, to produce correct colour rendition, to the positive material on which the print is to be made is known both as to exposure time and the colour of the printing light, applying colour correction filters to said control. patch until a match is achieved between the control patch with the colour filters and the standard patch and printing from the negative on to a positive while employing the said colour filters to control the printing light. As shown in Fig. 1, two identical lamps 15, 17 illuminate through grey wedges 22, 23 the control patch 20 to be compared and the standard patch 19, colour filters 21 being inserted in the beam from the lamp 15, and the light passing through the two negative patches is projected by lenses 16, 18 respectively to form grey patches on a ground glass screen 10, the control patch image by reflection from a mirror 13 and the standard patch image by transmission through a central aperture 14 in the mirror, both projection systems and the screen 10 being housed in lighttight casings. The grey patches on the screen are adjusted to equal intensity by means of the grey wedges and the filters 21 are selectively placed in the control patch beam until a colour match is achieved between the grey images on the screen 10, the grey wedges being adjusted to maintain the intensities of the images equal. The colour filters and the grey wedge density required to produce equality between the control and standard patch images are then noted, preferably on each negative in the roll, so that the printing light may be modified accordingly at the subsequent printing step. Fig. 3 shows a modification in which a single light source 27 and grey wedge are employed. The grey wedge is in the form of a disc 52 pivoted at 53 in the beam to the standard patch 47 and the colour filters are of sectorial form pivoted at 49, the filter sectors 30 each having one blank opening and four filters of different densities. The standard gray patch 47 is supported by an apertured tray 45 and the control patch 31 on a support apertured at 32. The light illuminating the two grey patches passes through lenses 28, 39 and is reflected by mirrors 35, 40 so that the standard patch beam passes through a central aperture 44 in a mirror 38 which reflects the control patch beam, both beams passing to the operator's eyes through a viewing lens 48. The filter sectors protrude from the casing of the apparatus and their edges carry filter density indications cooperating with a fixed mark on the casing. Instead of being carried on a rotatable sector, the filters may be arranged on slides or formed as density wedges in colour. The Specification as open to inspection under Sect. 91 comprises also the use of three separate correction comparisons of three separate single colour control patches with corresponding standard colour patches. This subject-matter does not appear in the Specification as accepted.