Luminaire and illumination system

A biodynamic luminaire comprising a light source to provide an illumination output and which, in use, at least to some extent mitigates the detrimental effect of artificial lighting on an individual subject in an illuminated environment, the luminaire comprises one or more integral sensors which detect or determine one or more behaviors and/or one or more psychological states of the individual subject, and a control unit which changes the illumination output based on data received from or by the one or more integral sensors, in which the luminaire comprises a first set and a second set of light-emitting diodes (LEDs), in which the first and second LED sets have a different colour temperature, and in which the LEDs are selectively energisable by the control unit to provide a desired overall colour temperature of emitted light whereby, in use, to provide tuneable white light at a sufficient output to beneficially affect the individual subject's circadian rhythm in the illuminated environment.