A projection system for image reproduction includes at least one lamp and sensor for generating a sensor signal for monitoring changes in the luminous flux generated by the lamp and for compensating these changes through a suitable control of the image reproduction. The projection system further includes a device for eliminating substantially periodic interference components from the sensor signal generated by the sensor. These interference components may be generated by an optical component such as a color modulator of the projection system. The projection system provides substantially interference-free compensation of fluctuations in the luminous flux generated by the lamp, for example, owing to an unstable arc discharge. Further, the positioning of the sensor in the projection system may not be critical.