Color printing control system and method

Abstract

A color printing control system for making prints from negatives having a color printer and a microprocessor. The output of photocells which read color negatives is applied to the microprocessor enabling it to calculate print time signals. These signals are applied, for example, to paddles and move them into the light path to terminate light exposure. A print test probe reads the density of the prints and is coupled to the microprocessor and forms a feedback loop which allows the microprocessor to adjust its internal values. In this manner, color balancing is performed and prints made from over and underexposed negatives have the same density as properly exposed negatives, without knowledge of paper characteristics and without operator setup calculations. This is achieved using the difference in density between a reference print and prints made by the system as a basis for calculating correction factors which are applied to such values as slope to cause subsequent print time signals to result in correct density. The system also corrects color predominance in negatives where the conventional integration to gray method would print incorrectly. In cases where color analysis indicates the possibility of exposure under tungsten or fluorescent light an operator prompt is provided allowing the operator to enable an appropriate correction.