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.