METHOD OF REGULATING INK SUPPLY IN PRINTING USING PLURALITY OF INK

PROBLEM TO BE SOLVED: To shorten a time required for attaining desired ink supply by a method wherein a monitoring signal of a place selected continuously is led out, the number of measuring places is increased when the monitoring signal exceeds a threshold set beforehand, and measured values of actual ink obtained at the places in the increased number are compared with a comparison signal. SOLUTION: A place being suitable specially for monitoring ink supply on a sheet 1 is selected and actual color positions of a small number of pixels 8 are monitored. When the actual color positions of the pixels 8 selected are within the region of a threshold set beforehand, printing is conducted continuously with a set amount of an ink setting element 12 with which the sheet 1 measured at that time point is printed. At the time when an actual value exceeds the threshold, the number of pixels 8 to be used for regulation is increased remarkably and supplied to a comparing element 10, a comparison signal on the output side of the comparing element 10 is processed to be a set amount in a regulating element 11 and supplied to the ink setting element 12 and thereby a film thickness of printing ink is changed.