I find that especially on center focus, when taking portraits in any light, but especially in lower light (I mean less than very bright, and not dark), a small move in the camera from say eye to forehead will bring on quite different settings, or at least a look in the photo that shows a different exposure (under/over). Ive never found this with my Nikons, and had this with my Olympus to the extent I got it fixed under warranty, but I can't replicate this on the Canon enough to warrant to take it in, though perhaps I should. If I take say 10 shots of a child, I tend to get this in certain conditions - but as I say Im troubled to replicate it. It could be that the sensor is overly sensitive, and doing the right job, but maybe missing exposures because its too slow. Any thoughts on this?