1. A method of displaying an image on a display device in a plurality of periods called sub-fields, wherein the display device is capable of generating in each of the sub-fields a respective illumination level, the method comprising the steps of: defining a set of combinations of sub-fields, each combination in the set corresponding with a respective illumination level of the display device; for each pixel of the image selecting from the set a particular combination of sub-fields in conformance with the intensity value of the pixel; and for each pixel of the image sending a representation of the selected combination of sub-fields to the display device for displaying the particular pixel, characterized in that the combinations of sub-fields in the set correspond with respective illumination levels that are uniformly spaced on a perceptual scale.