Originally Posted by dcstep
Hmm, I don't understand the problem I would expect that with that AF system that around 8 out of 10 would be sharp, not necessarily well composed, but sharp. When picking my "keepers" I look at them on my 24" screen at 100 or even 200%. For animals I look at the eyes. For your Blue Angels I'd look at the lettering or the pilot.
When your previewing it's tempting to look for the best composition and peak of action. Ideally that's what you want, but if it's not tack sharp, then it needs to be shit-canned, sometimes you don't see that until you're at 100%. Also, you need to look after-crop and make sure the detail is still there. You've got to be brutal in your self analysis. My goal is for all my images to stand up to a full-screen viewing. I'll often process a heavy crop and then dump it when I see it full-screen.
I've tried 61-point AF for fast moving, flying objects and it DOES NOT WORK. You get too many shit-cans. It works fine for cars driving down the street at normal speeds or runners or bikers coming toward you, but it starts grabbing at parts of birds or planes and doesn't focus exactly where you want. I use the single point with four points surrounding it. I think there's one with 8-points around a single that you might try.
Is there a remote control airplane club in your area? If so, shooting those guys is great, repeatable practice. Try several AF modes and make sure you ask them to fly their planes straight at you a bit. When reviewing results, make note of keeper rates for various modes. With 61-points you'll get some part of the plane in focus most of the time, but you'll find when looking at 100% that it'll be the tail, or a wingtip, etc. Even at f/8, that's often not accurate enough and wide open it'll be way off.
My next step is to work with developing a custom AF program for me and my two normal setups (500/f4 and 700/f5.6). The AF reaction times vary quite a bit between those two and deserve their own programs. I'm approaching 10,000 images with my 5D MkIII and think this extra refinement will improve my keeper rate even more. (I dump tons and tons of pix).
Yeah, neither do I. I haven't had a problem with sharpness on my other lenses, even in similar (but not so extreme) situations. Perhaps the 100-400mm needs some MFA? Or perhaps I just need to practice my skills more. I'll have to see what else is around town that I can practice on, before the winter begins.