Auto Focus

[Ptyler22]

Just had a random question pop into my head so I thought I would ask. The kit lens that comes with the 40d (28-135mm) isn't the fastest auto focusing, but not the slowest. I am going to a racetrack next weekend and I fear the auto focus isn't fast enough so I can try to manually focus but then all my shots may be slightly off. Do you think if I set it to just focus on the center AF point it will focus faster than if I had it set to all AF points? Thanks.

 

[Big Mike]

My initial thought would be to have the camera set to use all points and put it in AI Servo mode. This should help you track the subjects as they move in the frame.

You could also try pre focusing on a certain spot, then start shooting when the racers are coming to that spot.

You could also try tracking the subjects by panning the camera with the motion, this way, the subject should be in the same place in the frame, allowing for easier auto focus and some cool effects with background blur.

There are others here who shoot that sort of thing, maybe they will chime in.

 

[Overread]

I find that its easier to set the focus of aiservo and use only the centre focus point - that way you can keep the focusing point on the subject - using all the af points can lead to problems if the camera decides to focus on something else. Of course this does mean you need to keep a sharp eye on your subject - a monopod or tripod is helpfull for keeping your focus whilst panning - takes some of the weight out of the operation

 

[epp_b]

Use the centre as the focus point in continuous focus mode, make sure your focus is set approximately where you'll need it and it should be fine.