InfraRed cameras usually have a CDS sensor system that senses the light condition. When the environment is getting dark, the sensor will measure the condition, then calculate the data and send instruction to the control circuit. The IR lights on the camera will start to work according to the light condition. However, you will only get images in black and white once the camera is working on IR. The power of the IR light will be increased gradually till 100% when it is getting darker and darker.
Visit MyStore for IR night vision camera and Outdoor camera.