[1 of 1 customers found this review helpful]

By Yuki Hyo from Tokyo, Japan on 2/26/2008

Incomparable in terms of its choice of focal lengths, (especially at such a fast aperture) but doesn't hold a candle to either of Canon's 300mm L IS prime lenses (f/2.8 or f/4) in terms of AF speed, sharpness or saturation.
(I used it on a 1D Mk111 & 30D before parting with it) It was an interim purchase between owning an old 300mm f/2.8L USM Mk111 and the current IS version, but in all honesty, it's not as good as either (in any area apart from its marvelous zoom range). It's heavier, clumsier, scratches far too easily, doen't accept rear filters, has no stabilization, (what do you want for the price?) and there's something about that tripod mount-come-carrying grip that can only be experienced by handling it. In two words... it's odd! AND it can easily be cross-threaded if you're not really careful, so some kind of permanently mounted, after-market adapter plate is essential to my mind.
Shame really, because the lens shows a lot of potential. Perhaps a Mk11 version will close the gaps, but Sigma really has to do something about improving their lens durability. They all seem to mark far too easily.

For sports, brilliant..... for wildlife or birds, stay with your dedicated camera brand.