In low-light conditions, some IP security cameras use Automatic Gain Control (AGC) to artificially improve their “dynamic range” and produce usable images. AGC is basically a from of amplification where the camera will automatically boost the image received so that objects can be seen more clearly. In normal light conditions the camera will display a normal picture. However, when the light quality drops below a certain level the camera will begin to boost the signal to compensate for the lack of light.
The advantage of this technique is that your camera will produce images in much lower light conditions than standard. The downside is that the amplification is not only on the usable data in the image but also the background noise. This means that the more you amplify, the more noise you will see and the poorer the image quality will be.