An illumination system (1;30;40;60;70;90) for spot illumination comprising: a tubular reflector (3;31;61;91) with a reflective inner surface, the tubular reflector having an entrance aperture (9), and an exit aperture (10) being larger than the entrance aperture; and a light-source array (2;33;41;63;71;93) comprising a plurality of light-sources arranged in a physical light-source configuration to emit light into the tubular reflector at the entrance aperture thereof. The tubular reflector (3;31;61;91) comprises a plurality of reflective surfaces (14a-g) each being arranged to provide a primary mirror image of the light-source array, the primary mirror image having a primary mirror image light-source configuration; and the light-source array (2;33;41;63;71;93) is configured in such a way that, for each of the primary mirror image, at least half of all secondary mirror images of the light-source array resulting from reflection of the primary mirror image by the reflective surfaces (14a-g) exhibit secondary mirror image light-source configurations that are different from the physical light-source configuration.