What is the filter that moves in front of the lens sometimes?
The red O-ring in front of the lens is an IR-filter, it’s designed to move around depending on your shooting time. When the cam is powered up, the lens will move into position. When power is shut off, it relaxes. For daytime shooting, the filter will be in front of the lens to filter off the IR light which shall interfere your image otherwise (all commercial digital cameras have such a filter fixed in front of the lens); for nighttime shooting, the IR filter will be moved away from the lens to allow IR light pass through to give you the B&W pictures.
