An illumination system is arranged to output a light beam 415 for illuminating a scene 417. The system comprises a spatial light modulator (SLM) 407 arranged to receive incident light from light source 401/collimating lens 403 and to output light comprising a first component and a second component wherein the first component comprises light not modulated the SLM whilst the second component comprises light which has been spatially-modulated according to a hologram displayed by the SLM. Light output form the SLM may be directed to a reflector 409 to illuminate a scene 417. A control device (e.g. light tuning device 405) is operable to control the proportion of light output by the SLM that corresponds to the second component, thus controlling a ratio of output modulated light 713 to output non-modulated light 715. The light tuning device 405 may adjust a property of the incident light (e.g. polarisation, coherence or wavelength), such that incident light of a first property will not undergo modulation by the SLM, whilst incident light of a second property will undergo modulation by the SLM. Light 413 modulated in accordance with the displayed hologram may be steered to a predetermined region in the scene. The illumination system may be implemented in a vehicle to provide controllable headlight/headlamp illumination. Also disclosed are a related system and method wherein the control device is alternatively an SLM control device (705, figure 7) which adjusts allowable modulation levels of the displayed hologram.
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