I guess it depends on the aspect ratio of the cameras and your monitor. When I was looking at it they were all on main stream at 2688x1520 and the NVR is set to 3840x2160 on a 4K tv. If I change them to sub stream there’s bars on the side of the 3 large windows and less black bar on top and bottom of the two small windows. This is a higher end NVR that appears to be capable of displaying 9 4mp cameras on main stream. Displaying 16 and above switches to sub stream