GB1450488A - Light districution unit - Google Patents

Abstract

1450488 Photographic printing apparatus GROUP COLOR (W A) PTY Ltd 19 Dec 1974 [20 Dec 1973] 54889/74 Heading G2A A light box, which may form part of contact printing, enlarging and like apparatus, comprises a light source with a continously variable light filter, a matrix of light-transmitting rods or bundles of optical fibres 1 positioned to receive lighttransmitted by the filter and to transmit the light to the printing surface, and means mounted in association with each rod or bundle of fibres to control the amount of light transmitted therethrough. The box is used for shading negatives during printing, particularly colour negatives in aerial photography. As shown in Fig. 2, the apparatus includes a number of light-transmitting rods 11 made of e.g. transparent plastics material, which converge and come together in a spherical surface to receive light from a source (not shown), comprising a filter, e.g. a dichroic filter. The upper ends of rods 11 are opposite the lower ends of similar rods 12, and a shutter 14 (see also Fig. 3, not shown) is situated between each pair of rods 11, 12. Each shutter 14 is pivoted to cut off more or less of the light passing between the corresponding rods 11, 12. Shutters 14 are adjustable through linkage by discs 15 at the side of the box. The positions of disc 15 and the degree of filtering are quoted so that they can be reproduced at need. Each rod may be replaced by a bundle of optical fibres. In a printing unit, a length of roll film may pass over the light box for printing frame by frame. Light tight storage boxes (23), Figs. 4, 5, (not shown), may be provided for light-sensitive material. Paper for printing may be carried on an inverted roll easel (24) supported in a frame (25) slidable on tracks (26). The position of shutters 14 may be controlled electronically, and the filtering and shading information may be recorded on magnetic tape.