Abstract: A registration system is provided for maintaining accurate correspondence between an image on a moving substrate and the action of an operating element with respect to the substrate. A comparison optical device is mounted such that the timing marks pass in correspondence with the comparison optical device when the substrate is moving. A detector senses the intensity of radiation reflected from the substrate through the comparison optical device and generates a firing signal based on the reflected radiation intensity. The firing signal is provided to the operating element to activate it in correspondence to the passage of the timing marks.