Dirt bike shosts and a question

First off this is my first post of shots in the forum. Been lurking for a while, but thought I'd put some up for comment, so feel free to fire away. Let me know if the images are too big and I'll resize them.

http://bmaziarz.home.b​resnan.net/bike1.jpg

http://bmaziarz.home.b​resnan.net/bike2.jpg

http://bmaziarz.home.b​resnan.net/bike3.jpg

http://bmaziarz.home.b​resnan.net/bike4.jpg

[edit] Maximum size for inline images is 800 pixels along the longest edge

And now the question. Haven't had a whole lot of experience shooting dirt bikes before and even though I had AI focus set on my 5D I was finding that I was losing a number of shots with focus problems as my 100-400f/4L wasn't able to focus quick enough as the bikes appeared over the jumps. I tried pre-focussing on the edge of the jump to give the lens a bit of a head start and that helped quite a bit, but I was wondering if the pros have any other suggestions to up my keeper rate?

Cheers
Ben

Change your focus points to center point only and that will help speed up focus. Shooting blind like this is a challenge at the best of times. Best is to prefocus, lock the focus and as the riders enter the zone snap the picture. Stop down to Increase your DOF to help keep in focus.

PS Nice job on these ones.....

Thanks for that Jeff. I'd already swapped to the centre point, but I'll try your other suggestion next time I'm out there.

Cheers
Ben

they look awesome.. nice job

brilliant! So sharp and colorful.

Nice shots. Try posting smaller images - atleast for me, they were bigger than my screen. Plus I think there's a limit of 100k per image on the forums?

Ooops, will do in future. Thanks admin.

Nice shots. To me though they appear to be over sharpened.

If you are having trouble with focus you might want to consider a different vantage point where you can track the bike and then shoot once they are in the air. Trying to catch something moving this fast coming over a jump is going to result in some missed shots.

Thanks for the comments SSim. I have certainly sharpened them and only did so quickly without really looking to closely. I didn't notice any halos when I did so though. Are you seeing problem areas where there are artifacts from sharpening?

I'd be interested in hearing what settings you normally use for sharpening in PS. I'm always open to learning something new!

Edit: Actually looking at them now you are correct. There is some aliasing along some of the lines on the outfits on the riders. I'll have to redo them and back off the sharpening a bit. Thanks.

If you use AI servo and select center focus point only, if the subject moves to far to the side of the frame it will loose lock.

nice shots