Printer for recording on a moving medium

A method for forming a pixel having a predetermined density onto a sensitized recording medium moving in a length direction energizes a pixel exposure source to begin exposure at the leading edge of a pixel and for a first predetermined time interval. The pixel exposure source is de-energized for a period depending on the predetermined density and on media transport speed, then re-energized at the termination of the period. The pixel exposure source is then de-energized at the end of a second predetermined time interval to terminate exposure at the trailing edge of the pixel, whereby spatial dimensions of each pixel are maintained at variable transport speed or density of pixel.