Colour and the Characteristic Curve

Paper presented to the Hurter and Driffield Centenary Colloquium, Bath, 2 November 1990.

Abstract

Characteristic curves of colour pho-tographic materials are measured with red, green, and blue filters so as to evaluate their three differently sensitized layers by means of three curves. When pictures are projected in dark surrounds, their apparent contrast is reduced, so that their objective contrast has to be raised to produce pictures of apparently correct contrast. Characteristic curves of colour materials intended for projection in dark surrounds enable this increase in contrast to be measured and controlled. The cyan, magenta, and yellow dyes used to form images in colour materials have unwanted absorp-tions in parts of the spectrum outside their main absorption bands; these unwanted absorptions are corrected by the use of coloured couplers and inter-image effects; characteristic curves provide indispensable insights into these processes.

Notes

Paper presented to the Hurter and Driffield Centenary Colloquium, Bath, 2 November 1990.