When the security lights come on then the camera will probably be blinded until it compenates for the sudden change in brightness. This means you will lose video for a while. Depending on the camera this could be as long as five seconds at the very moment you need to see what is happening.
Providing there is enough illumination ( light or infra red ) for the camera to see then use PIR motion detection to mark the recording and leave the light level as is until a clear image of the motion and people has been recorded.
