Abstract: A plate cylinder of an offset printing press is adjustable. A motor has an output shaft operatively connected with the plate cylinder to, when driven, adjust the position of the plate cylinder. A tachometer provides a speed reference signal indicative of the rotational speed of the plate cylinder. A register mark error sensor provides an adjustment control signal indicating that the plate cylinder should be adjusted. A computer responds to the speed reference signal and the adjustment control signal to control a DC drive. The DC drive drives the motor at a speed which varies with the rotational speed of the plate cylinder. The plate cylinder is thereby moved to a desired position at a rate which is a function of the operating speed of the printing press. The plate cylinder is moved to the desired position at a slow rate when the printing press is operating at a slow speed and at a fast rate when the printing press is operating at a fast speed.