from my own experience, i know of people who have used the Sigma and Tamron 70-200 havd have found the autofocus on both to be very slow, inadequate for sports. i personally own a Sigma 50-150mm f/2.8 which is the equivalent of 80-210 on a full frame camera. i absolutely love this lens, but if you read brian's review or others online, people have had problems with improperly calibrated versions that front-focus, so buyer beware with that. as far as fast, wide zooms, i've heard nothing but great things about the Tamron 17-50 f/2.8, however this is also a digital only lens that wont fit on a film camera. hope this helps some