A method of controlling a solid state lighting apparatus, the method comprising: providing a first model of an operating parameter of the solid state lighting apparatus based on a plurality of operating conditions of the solid state lighting apparatus for a target light output characteristic of the solid state lighting apparatus; controlling an operating parameter of a first plurality of solid state light emitting devices of the solid state lighting apparatus in response to a change in at least one of the plurality of operating conditions in accordance with the first model; measuring a light output characteristic of the solid state lighting apparatus; comparing the measured light output characteristic to the target light output characteristic of the first model; characterised in that the method comprises further, in response to a difference between the measured light output characteristic and the target light output characteristic of the first model, providing a second model of the operating parameter of the solid state lighting apparatus based on the plurality of operating conditions of the solid state lighting apparatus for an adjusted target light output characteristic of the solid state lighting apparatus; and controlling the operating parameter of the first plurality of solid state light emitting devices in response to a change in at least one of the plurality of operating conditions based on the second model; wherein the first model and the second model of the operating parameter of the solid state lighting apparatus each comprises a plurality of control points of a Bézier surface that relates the operating parameter of the first plurality of solid state light emitting devices to the plurality of operating conditions of the solid state lighting apparatus for the respective target light output characteristic. providing a first model of an operating parameter of the solid state lighting apparatus based on a plurality of operating conditions of the solid state lighting apparatus for a target light output characteristic of the solid state lighting apparatus; controlling an operating parameter of a first plurality of solid state light emitting devices of the solid state lighting apparatus in response to a change in at least one of the plurality of operating conditions in accordance with the first model; measuring a light output characteristic of the solid state lighting apparatus; comparing the measured light output characteristic to the target light output characteristic of the first model; characterised in that the method comprises further, in response to a difference between the measured light output characteristic and the target light output characteristic of the first model, providing a second model of the operating parameter of the solid state lighting apparatus based on the plurality of operating conditions of the solid state lighting apparatus for an adjusted target light output characteristic of the solid state lighting apparatus; and controlling the operating parameter of the first plurality of solid state light emitting devices in response to a change in at least one of the plurality of operating conditions based on the second model; wherein the first model and the second model of the operating parameter of the solid state lighting apparatus each comprises a plurality of control points of a Bézier surface that relates the operating parameter of the first plurality of solid state light emitting devices to the plurality of operating conditions of the solid state lighting apparatus for the respective target light output characteristic.