shinksma wrote in post #14802772
Thanks jdhill! Yeah, I like my 100-400L. Sometimes the AF frustrates me (slow, perhaps easily confused, or maybe that's the T3i)e.
shinksma
EDIT: I'm sorry, I was so intent on writing what I did below that I forgot to say what good shots they all are! I use my 100-400mm also for that, so I can appreciate what you have accomplished. 
Now that you bring that up, I remember when I was using my 100-400mm L on my T2i I had a hard time figuring out why 'all of a sudden' now that I have a better camera, my shots were not as in focus as they were...
What I ended up doing was to 'always' use 1.8m setting instead of the 6.5m, as weird as it sounds, I could get a LOT better focus on birds way up in trees that were normally not that sharp. (Before that I had a XSi and it had to be on the 6.5m setting to work properly for any distant shots)
I upgraded to another camera now, but it's not the case on that, it has to be on the 6.5m on all long shots.
So, it appears (for me at least) to only be that way for my T2i, I guess that stranger things have happened.
As strange as it may sound, try that and see if that is what the deal is for you too.
Randy