A multi-viewer autostereoscopic display system having a viewing field across which the system is capable of steering exit pupils, in each of which a viewer is capable of viewing an image for a selected eye. The system comprises an image forming device for generating an image by selective attenuation of radiation, an array of optical elements for projecting radiation towards the image forming device, and an array of radiation output positions for outputting radiation into the array of optical elements. Sets of radiation output positions respectively extend over a horizontal width associated with an optical element and have selectable positions such that an exit pupil is formed in a selected part of the viewing field. Each set of radiation output positions has an associated aperture for limiting the horizontal extent of the light projected from the radiation output positions. The apertures have a horizontal extent which is less than the horizontal width of the associated set of radiation output positions.