System for determining a change in a room, the system comprising illuminants , suitable for emitting light; control means , suitable for controlling the light emission of the illuminant ; measuring means , suitable for determining a light intensity, an evaluation means suitable for evaluating the determined light intensity and for generating a switching signal for the control means based on the evaluation of the light intensity; and the evaluation means being designed, starting from a determined light intensity which forms a reference for the determination of the change in the reflection conditions in the room illuminated by the illuminant , to detect a change of an object in the room at least at a first point in time at which the illuminant does not emit any light, and a light intensity at least at a second point in time at which the illuminant does emit light, so that the change in the object in the room is determined by detecting a change in the reflection conditions in the room by means of the determined light intensity at the at least one second point in time, the system being a component of an illumination system and the measuring means being assigned to the illuminant and arranged within or on a housing of the illuminant, the measuring means comprising a daylight sensor; and the system being characterized in that the control means is configured to start a burst operation of the illuminant when the daylight sensor determines a light intensity below a daylight threshold, and the illuminants are switched to inactive in order to check the reflection properties of the room at regular intervals during said burst operation. illuminants , suitable for emitting light; control means , suitable for controlling the light emission of the illuminant ; measuring means , suitable for determining a light intensity, an evaluation means suitable for evaluating the determined light intensity and for generating a switching signal for the control means based on the evaluation of the light intensity; and the evaluation means being designed, starting from a determined light intensity which forms a reference for the determination of the change in the reflection conditions in the room illuminated by the illuminant , to detect a change of an object in the room at least at a first point in time at which the illuminant does not emit any light, and a light intensity at least at a second point in time at which the illuminant does emit light, so that the change in the object in the room is determined by detecting a change in the reflection conditions in the room by means of the determined light intensity at the at least one second point in time, the system being a component of an illumination system and the measuring means being assigned to the illuminant and arranged within or on a housing of the illuminant, the measuring means comprising a daylight sensor; and the system being characterized in that the control means is configured to start a burst operation of the illuminant when the daylight sensor determines a light intensity below a daylight threshold, and the illuminants are switched to inactive in order to check the reflection properties of the room at regular intervals during said burst operation. <EOS>