I'm wondering how effective you rate the AI Focus / AI Servo modes on the 40D. I'm shooting kids on a swing set, and my hit rate is about 1 in 5.


I stand in front of the swing set; the kids move near to far through the frame. I frame the shot in AI Servo or AI Focus, half-press the shutter and follow the swing while I wait for focus. The problem is, much of the time I miss when the child is in focus - by the time I press the shutter release all the way down, focus is gone.


I've tried AF at the apex of the swing (generally where I want to capture), then switching to MF and taking shots this way, with a little better hit rate. I've also tried One Shot AF with so-so results, again about 1 in 5.


Is this just a tough shot to get, or am I misusing the AF modes? Is AF the right approach, or should a photographer expect to MF shots like these and get mostly "hits?"


So far I've used 40D, 70-200 2.8 IS, ~ 1/250. The hits look great; I'd like to get more of them!


Thanks for any thoughts you'd like to share...