Patent GB-402902-A (GB)
Abstract: 402,902. Colour photography. I. G. FARBENINDUSTRIE AKT.-GES., Frank. fort-on-Main, Germany. Sept. 8, 1932, No. 25055. Convention date, Sept. 8, 1931. [Class 98 (ii).] Projection-apparatus for printing on non- lenticular sensitive material separate monochrome records from a multicolour record taken on a linear lenticular film in a camera having an objective fitted with a colour-band filter comprises a projecting objective whose focal length may differ from that of the taking objective, and whose aperture is not greater than that of the taking objective, and a stop associated with the projecting objective and producing an entrance pupil whose distance from the lenticular film is equal to the distance of the colour-band filter or its virtual image from the lenticular film during taking, and whose breadth is not greater than that of a single colour area of the taking filter, or of its virtual image as seen from the plane of the film in the camera. In the printing process, if the aperture of the objective is sufficiently wide, the monochrome records are printed in succession by displacing the stop step-wise across the objective so that the centre of the entrance pupil which it forms coincides in the successive printing positions with the points corresponding to the centres of the separate areas of the colour-band filter or its virtual image in the camera when taking the lenticular film ; but if an objective of small aperture is used, either the objective is displaced with the stop, or the objective and stop remain stationary, and the negative film is rotated stepwise about an axis in its own plane, parallel to its edges and passing through the optical axis of the projection system, into successive printing positions in which the lines which joined its centre to the centres of the colour areas of the colour band filter or its virtual image when the film was in the taking camera pass through the centre of the entrance pupil of the projection objective. Fig. 2 shows apparatus for printing the records from a lenticular original 1 on to a sensitive film 11 with unit magnification. The projecting objective 4 has an aperture comparable with that of the taking objective, but is of different focal length, and has a stop 10 whose virtual image lies at 10<1> when seen from the film 1. The system is adjusted so that the distance a of the image 101 from the film 1 is equal to the distance of the colour band filter or its virtual image from the film 1 when the film was in the taking camera ; and the breadth of the aperture of the stop is so chosen that its breadth in the virtual image 10<1> is not greater than the breadth of one colour band of the filter, or its virtual image, in the taking camera. In Fig. 2, the stop is in position for printing one of the records of a tricolour image, and it is displaced for printing the remaining two records in the manner above-described so that its centre coincides in turn with the points 7<1>, 8<1>. A similar apparatus is described for printing enlarged records. Fig. 4, shows a modified apparatus using a small objective 4 with a stop 10 behind it. In this case, the stop itself forms the entrance pupil, and its distance a from the film 1 and its breadth are determined as before. The objective and stop are moved together into the successive printing positions previously defined, in which the centre of stop coincides with points 6<1>, 71, 8<1>, on lines drawn from the centre of the film 1 when in the taking camera to the centres of the colour bands of the taking filter or its virtual image. Instead of displacing the optical system in this manner, the same result may be achieved by placing the objective and stop in the central position for printing the first record, as shown in Fig. 5, and then rotating the film 1 about an axis passing through its centre 9 parallel to the lenticles of the film so that the lines joining the centre 9 to the points 6<1>, 8<1> previously defined pass centrally through the system in succession for printing the remaining two records. In all cases, the sensitive film 11 must be displaced if necessary so that it receives each partial image centrally, and in the case shown in Fig. 5, it should be rotated, before printing each image, in the same manner as the negative, in order to preserve uniform sharpness of focus of the images.