A light system for medical photodynamic applications comprises an incoherent light source emitting a light with a power and a light guide which has a distal end and an entrance interface. The entrance interface and the light source have a position relative to one another and are able to be positioned relative to one another. The light system further comprises a luminous power meter for measuring a luminous power emitted at the distal end of the light guide, a motorized positioning unit for positioning the entrance interface and the light source relative to one another, and a control unit which controls the positioning unit as a function of the luminous power measured by the luminous power meter.
