A method for controlling a digital display device of a head or helmet-mounted display system and a head or helmet-mounted digital display system implementing the method are provided with the aim of controlling the display device in such a way as to reduce the effect of dynamic false contouring on the quality of a displayed image. According to the method, received image data defining brightness levels according to a scheme of light pulse modulation based upon binary-weighted pulse durations are converted into a data defining a sequence of pulses of binary and non-binary weighted duration in which the highest value weighting represents a pulse of a duration less than half the total duration of illumination required during an image refresh period to achieve a pixel at the highest brightness level. In a further embodiment, the weighting of highest value represents a pulse of duration less than one quarter of the duration required for highest pixel brightness.