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Abstract
A description is given of on enlarger designed for making colour prints. The colour of the light illuminating the negative is continuously variable by means of cyan, magenta, and yellow sliding filters, the light from which is mixed by means of a box of mirrors; the unwanted absorption of one of these filters is compensated for by means of an auxiliary sliding filter. Monitoring for colour balance is carried out by allowing light from the negative to fall on barrier-layer cells covered by red, green, and blue filters; monitoring for density is carried out by means of an unftltered cell at the paper plane; a galvanometer is used to measure the photo-currents. The monitoring system can be used either as a calibration for the sliding filters, or as a means of making prints whose integrated light approximates to grey. A potentiometer net-work provides controls for paper speed and for “plus and minus” correction in both density and colour according to the subject-matter in the negative.