Since in most CMOS and sCMOS image sensors the readout is row-oriented, the readout time for a whole image or frame is one of the major time dominating factors. While the rolling shutter very much looks like the old slit curtain shutters, the other type of shutter, the global shutter, is more like a central shutter or near to the former interline transfer CCD shutter, which allowed for very short exposure times.
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Albert Einstein