here lately ive been struggling with my sigma 24-70 2.8 to get sharp photos. it seems as though the af hunts a lot and will go from one end of the focus spectrum, to the other, twice before deciding what to focus on, and then when it does and i snap a pic, its not sharp. while using manual focus and i get the focus confirmation and get the same results, but ive noticed if i get that confirmation, and back off the focus ring a tad, snap a pic and check it on the pc its more sharp then where the AC is set. have i changed some setting accidentally? it wasnt like this when i bought it, i checked my 70-300 f4 lense and it looked more sharp then my fast lense so i thought maybe it was the lense and not the camera, but now im just looking for any info or advice then can help me remedy the problem, im shooting on a 20d canon. i consider myself a newb so if there is something super simple that i might of done, dont hesistate to call me out on it.