Boogieman, Thanks for the response. All four cameras are set to VBR but respond as I mentioned in my original post. When I change the low bit rate camera from VBR to CBR the bit rate does come up to ~75% of the other three cameras. Changing the other three cameras to CBR from VBR makes no difference in their bit rates. As for the night time differences I have put the suspect cameras in a dark room and compared them to a "normal" camera. I still get the brighter central image with the suspect cameras. I'm beginning to think they are just more sensitive but I don't understand the bit rate differences.