Improved Color Separation of Transparencies by Direct Screening

Abstract

The production of halftone separations directly from original colour transparencies has for some time held interesting prospects. It can offer the fastest, most economical, and most reliable method of colour reproduction. In the lost few years many improvements in photographic materials and equipment for the graphic arts industry have made direct screening more practical. The need for long exposures has been minimized by high-efficiency, condenser-type enlargers with pulsed-xenon sources, improved contact screens, and faster, panchromatic, Kodalith-type films. The advent of dye-image masking films has not only simplified colour correction but also contributed greatly in reducing the problems arising from the Q-factor of silver films. The steps involved in a direct-screening system using improved Kodak Grey Contact Screens, Kodak Tri-Mask Film (Estar Base), and Kodalith Pan Film (Estar Base) have been analyzed and the results disclose the simplicity of the controls required for excellent photo-mechanical reproduction. A disc-type computer is described which affords rapid determination of the exposure conditions for proper tone reproduction and balance in the halftone set of separations. Colour reproductions produced by the new, direct screening method are shown, together with pertinent data for their critical evaluation.

Notes

Paper presented at a Symposium on “Photographic Materials and Processes in the Printing Industry”, 4–6 December 1963, in London.