Electrical apparatus for comparing dark and light areas on a substrate and which substrate is in a liquid

摘要

This invention is directed to a new apparatus to assist in the making of negatives. If the negatives are screen separation negatives, then the screen separation negatives can be used in the making of printing plates. For colored prints there are a plurality of screen separation negatives and a plurality of printing plates. With this apparatus it is possible to develop a screen separation negative to realize a predetermined dot structure. As a result, in a plurality of screen separation negatives there is a more uniform dot structure. With a more uniform dot structure in the screen separation negative there is a more uniform dot structure in the printing plate and therefore a more uniform printed color print. The apparatus indicates when the dot structure, viz., opaque area and clear area, on the developing screen separation negative reaches a predetermined standard for dot structure or a predetermined standard of transparency to light. This apparatus can be used with a continuous tone negative in the test for an opaque area and for a clear area.