A process for measuring the amount of mis-registration between first and second print heads of a digital printing machine and adjusting the print data sent to the machine. The process comprises a step of printing a calibration test page comprising overlapping registration targets created by the first and second print heads. The overlapping registration targets each comprise a target region comprising X and Y co-ordinates. The process further comprises a step of scanning the calibration test page to produce a bitmap image. The process further comprises a step of processing the bitmap image to produce a mis-registration score for each target region. The process further comprises a step of producing X and Y registration correction amounts for the second print head based upon the mis-registration scores. The process further comprises a step of adjusting the print data to the second printhead based upon the X and Y registration correction amounts.