Patent GB-483817-A (GB)
Title: Production of cinematographic effects in colour and means therefor
IPC: G03B33/08
Filed: 1936-07-25
Abstract: 483,817. Colour kinematography. HILLMAN, A. G., and JOHNSON, G. H. July 25, 1936, No. 20672. [Class 97 (i)] Three or more colour-record images arranged in sequence on a film are taken in succession during each stationary period of the film, and either without overlap of successive exposures or with such overlap ; in the projection of positives therefrom, two or more images may be projected simultaneously, each being projected twice ; shutter constructions for use in the camera, and a rotary filter for use in the projector are described. The exposures may be effected by means of a single rotating shutter having angularly-displaced arcuate slots at different radial distances from its centre, Fig. 2 shows an alternative shutter construction comprising two discs 15, 16 geared to rotate in opposite directions, each being formed with an exposure slot 24, 25, and with marginal notches 26 co-operating for exposure of the middle image. A modification is described in which one of the discs has a marginal notch for exposing an end image, and the other disc has a marginal notch and an arcuate slot for exposing the other images. As shown in Fig. 8, exposure of the middle image is effected by an oscillating shutter 110 moved by a cam 111 engaging a roller 111c on the shutter arm, against the action of a spring 111b ; in a modification, the shutter 110 may be reciprocated horizontally by a crank arm to effect exposure through a vertical slit therein. Fig. 9 shows exposure apertures 113, 114, 115 in a sector 112 oscillated by a cam 119 through a lever 117 and a link; a rotary sector 116 covers the apertures during the film shift. The shutter apertures may be such that the exposures are separated by a time interval, are coterminous, or overlap, the overlapping being such that the first and third exposures do not overlap. The exposures may be of different durations, and may be made in a three-image gate by three lenses having a light-dividing system before them such as is described in Specification 478,500, and a focusing system as described in Specification 483,820. Film shifts of three images at a time may be effected eight times per second by an accelerated-shift mechanism such as is described in Specification 473,819, and a carrier for two or more sets of filters may be provided, as described in Specification 483,079. The middle image may be exposed through a red filter so that, during projection, the simultaneously-projected images which were separated by a film shift during taking shall be the blue and green images respectively. Projection may be effected by a standard monochrome projector having a single-image feed mechanism, a two-image gate, a pair of lenses projecting superposed images, and a filter disc comprising blue filters 92, 89, red filters 90, 93, and green filters 94, 91. The filters may be separated by opaque sections, or by coloured light-transmitting sections 95, 96 having colours different from those of the adjacent filters. The blue filter 92 and green filter 91 may contain green and blue sections 98, 99, respectively, to cause colour confusion when the images which are separated by a film shift during taking are projected together, and colour-confusion sections may also be provided in the other filters ; the filter disc may be used without a separate shutter. More than two images may be projected together. Complete heliochrome positives may be prepared from the negatives. Suitable exposure times and filter combinations are set out in the Specification.