Partial Exposure. If a camera flash goes off in the shot, the quick nature of the flash may only be present for some of the rows of pixels in a given frame. So as an example, the top 1/3 of the picture may be brightly lit by a flash, while the bottom 2/3 of the picture is dark and unlit as the time it took for the flash to occur was only sequenced in a short amount of time as the CMOS imager sequences a frame. The difference between the two distinct parts of the frame can look odd. Similar problems can arise with emergency vehicle lights, some fluorescent lighting, or any extreme situation where very fast motion or very fast bursts of light are seen in the time between when the CMOS chip sequentially records a frame.