A digital LED printer is described which uses an improved control architecture to enable multi-exposure levels and multiple gray levels for a LED printbar. A plurality of LED chips are aligned in a row to form a printbar (27) of a length sufficient to expose the width of a recording medium, such as a photoreceptor drum or belt. Each LED chip has an associated driver chip (40) which controls the individual LED on/off time as well as the magnitude of current applied to each LED so as to maintain uniform exposure of each energized LED. The LED on/off time is controlled by selection of one of a plurality of two bit or four bit gray level strobe signals, which are decoded (38) according to system logic. The LED characteristics are measured (80) and stored (42) in a pre-operational mode to measure differences in gain characteristics; correction signals for each LED are then stored in memory and downloaded into the LED drive circuits at the end of each recorded line.