A light therapy system (12) for administering a controllable melanopic luminous exposure includes a lighting assembly (16) for producing a light output (68) having a configurable illuminance and color temperature. Based on a received target melanopic luminous exposure a controller (24) of the system constructs a suitable control schedule (71) for controlling parameter levels of the lighting assembly over time such that in total over a defined treatment period (78), the indicated target melanopic luminous exposure is delivered. In constructing the control schedule, the relative melanopic sensitivity of humans to light of different color temperatures is taken into account. The color temperature of the administered light is accordingly controlled such that after adjusting for color, the delivered luminous exposure conforms to the input exposure target.
