a system and method for reducing pulse width modulation contouring artifacts . each input intensity value is translated to at least one non - binary bit pattern for display . many of the input intensity values are translated to at least two alternate non - binary bit patterns . the alternate codes are used to smooth the transition between intensity codes as major bits are turned on . the smoothing occurs by the gradual transition from codes that do not use the major bit to codes that do use the major bit . typically the alternate codes are selected based on the location of the pixel in a spatial pattern and the alternate codes are spatially alternated from one pixel to the next . other embodiments temporally alternate the codes from one period — typically a frame period — to the next . still other embodiments alternate the codes both spatially and temporally .