A directional display comprises a display arrangement such as a spatial light modulator 2 and a rear parallax barrier 6 illuminated by a suitable backlight 1. The spatial light modulator 2 and the parallax barrier 6 cooperate to produce Fresnel diffraction which results in spatially non-uniform brightness across viewing windows of the display. Also, where the spatial light modulator 2 has pixels of non-constant vertical aperture, further variations in the intensity profile at the windows occurs. In order to compensate for this, a mask 21 is provided, for instance between the parallax barrier 6 and the backlight 1. The mask 21 cooperates with the parallax barrier 6 to produce an intensity pattern having variations which are the inverse of the variations in intensity pattern produced by the parallax barrier 6 and the spatial light modulator 2. The variations are superimposed and substantially cancel each other out so as to result in viewing windows which have substantially uniform light intensities.