A possible reason why DSLRs exhibit more flicker than compacts could be if their physical shutters are locked to 1/3 ev exposure steps while electronic shutters on compacts are allowed much smaller steps in auto modes. Exif doesn't reveal if this is the case, so here I test how smooth the SX100 in auto (P) mode varies the shutter speed as compared to the S3 forced to do 1/3 ev steps because I have it in Manual (M) mode, adjusting the exposure time manually along the way. As can be seen, 1/3 ev steps are quite visible, and it can be concluded that these compacts use much smaller steps in at least shutter speed even though they only write 1/3 ev values to exif. Apart from the 1/3 ev steps on the S3, both cameras exhibit a little flicker as well, the SX100 being worse. It also dropped out of focus even though AF lock was activated. :-|
EDIT: Now that more accurate exif info is superposed it verifies the much smaller steps - about 1/32 ev (with some odd variations).