The camera I have is an Olympus digital Compact, the in built IR blocking filter has been removed and instead of replacing it with a IR filter in camera , screw on IR filters are screwed to front lens, means I can change the strength by adding a stronger filter such as 850nm which blocks all visible light, the filter from memory, which at the moment not working to well lol (memory I mean) is a 720nm This blocks around 90 percent [ithink)