An autostereoscopic 3D display includes a spatial light modulator, for instance of the liquid crystal display type. A backlight and a mask form a plurality of light sources which are imaged by a lenticular screen at first notional viewing windows. A parallax barrier controls the visibility of pixels of the spatial light modulator to form second notional viewing windows. The display forms actual viewing windows whose lateral extent is equal to the product of the lateral extents of the first and second viewing windows and is less than each of these lateral extents.