A display device is provided that comprises a liquid crystal display panel (2) for displaying an image by spatial light modulation. The image is represented by a plurality of image elements each having an image data value (7). The display device further comprises a display controller (1) arranged to determine a signal voltage to be applied to the panel (2) for each image element in dependence upon its image data value (7) and a secondary data value (8) for the element, there being a predetermined mapping between the data values and the signal voltage. The secondary data values (8) are arranged to vary across the image so as to introduce variations in luminance as a result of the mapping. The mapping and secondary data values (8) are mutually arranged to take account of the signal voltage to on-axis luminance response of the panel (2) so that the luminance variations introduced on-axis tend to balance locally through spatial averaging to, and hence would not be perceivable by, an on-axis viewer (3). The panel (2) furthermore has a non-linear off-axis luminance to on-axis luminance relationship, so that at least some of the luminance variations introduced off-axis do not balance locally through spatial averaging to, and hence would be perceivable by, an off-axis viewer (4).