Series 9000™ Darkroom Photoelectric Sensors are designed for use in areas where you must sharply reduce the emission of visible light, such as in the manufacturing of photographic films and papers. These ON/OFF sensors reduce visible light emission to less than 0.03 millilux measured 25 mm (1 in.) from the sensor. The Series 9000 darkroom sensors use a status indicator source with very little visible light emission.