Lets Bring it all together Which 70-200 2.8

I have read several reports that claim that the F4 IS version is the sharperst, by a very slim, probably-doesn't-matter margin.

That said I recenlty swapped that for its big brother, the F2.8 IS primarily because I wanted to use either the 1.4X or 2X TC...or both, without losing out on AF.

I think all iterations of that lens is superior in IQ...can't go wrong whichever one you go with!

Croasdail wrote in post #2616874
Adding to what David said, there is a HUGE speed difference with the Sigma on a 10D/20D vs. a 1D body. Why, I don't know. But on mine, it is like night and day. I have almost never seen the Sigma hunt on a 1d, where with the 20d, it doesn't happen often, but it does happen. I have had the Canon lenses hunt with the 20d, but less so then with Sigma. It hasn't happened often enough to be an issue with either, but it is still there.

Did the hunting occur in low light or was it in a contrast situation say shooting a bird in flight with a clear sky.