Hi Tom,

I use AF most of the time when shooting mountain bike racing. Sometimes I will pre-focus on a spot then turn AF off, but that's not what I did for all of the shots in the smugmug album or that particular shot. Here are the details - technical and composition that I used for that particular shot:

1. Canon 5D III set to aperture priority set at f/4, full frame evaluative meter, auto white balance, 6fps, ISO 200, AF Servo mode with sub mode selection optimized for fast moving sports (can't remember which of the six options that is, but I selected it)

2. Canon 16-35mm f/4L lens

3. Get to a spot on the course and pick out one to three "framing areas" in which to shoot a rider. I think I had two spots for that location. Pay attention to sun angle and where the subject will be in the frame. Sometimes I will take a few test shots with a "Roving Marshall", observer, or course sweep in the frame.

4. Pick an off-center AF point that provides a good composition for each framing area - we're shooting photos here, not targets and I can't stand the "bull's eye" style of photography.

5. Put the AF point on the rider before he/she enters the desired framing area, push the shutter button 1/2 way down to AF track, shoot a few frames in the target area, continue tracking the rider to the next target area, adjust zoom if necessary, and shoot a few more frames in the next target area. Some people like to use the thumb activated AF activate button on the back of the camera, but I prefer to slave AF activation to the shutter button. I've also found that short, controlled bursts are the best way to shoot at 6fps for me. If you just hold down the shutter button and hope for the best it is difficult to follow the subject with the mirror going up and down. It also increases your odds of losing AF tracking because the selected AF point may move off the rider. Besides it's a freakin camera, not an Uzi It's best to learn your sport / subject and know how to predict action rather than to just hose them down and pray for a good frame or two out of a bunch of crap frames.

A big advantage to using AF tracking for mountain bike racing is unexpected stuff happens regularly as shown below.

Cheers,

Phil