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Originally Posted by Roy C
...recently I have been trying A1 Servo for almost all my bird shots and as it seems to work ok. I think I am right in saying that A1 Servo only uses the centre focus point for the intial 'lock' but after that it will use all availble focus points to keep track of the subject.
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What you are saying about how AI Servo uses the AF points is correct, certainly with my old faithful 10D. Because of the way it works, I would imagine that using AI Servo all the time with birds could cause you problems at times?
Most agree that getting the bird’s eye in focus is critical, and when using a telephoto lens with large aperture, the depth of field is very shallow. As far as I understand it, if with AI Servo selected you focus on the eye, and part of the bird is
in front of the eye, another AF point will take over and critical focus will move away from the eye. Also, if after focusing on the eye you move the camera to recompose the shot, focus may shift from the eye, especially if there are other objects (leaves, branches, etc) in front of the bird’s eye.
Have you experienced these problems? I’d be interested to know how you get on with AI Servo and birds.