A high-resolution ink jet printer includes a drum supported for rotation about an axis, substrate positioning means for positioning a substrate sheet on the surface of the drum to receive a printed image, carriage means movable parallel to the drum axis, printhead means supported on the carriage means and having at least one array of orifices disposed in spaced relation to the surface of the drum for projecting ink drops onto a substrate sheet carried by the drum, drive means for driving the carriage parallel to the axis of the drum, encoder means providing a train of signals at a rate dependent upon the rate of rotation of the drum, and control means for controlling the projection of the ink drops from the printhead means at a rate that depends on the rate of signals received by the control means.