@carlo: tried the tamron 28-75 before pero wala kaau ko naka observe sa iyang sharpness at every focal length. pero ang mga tamron jud nuon are sharp lenses jud even at wide open. with regards to tele, i've experienced using the sigma 70-200 HSM II sauna, at wide open from 70mm to something like 135mm madala ra ang IQ, pero at 200mm wide open, soft au. para na nako ha. but then again, "sharpness is in the eyes of the beholder". hehe.