Bird in flight question

[HDNitehawk]

Joel,
thanks for the explanations.

If you use the center focus point only in AI Servo, will the camera still use the other focus points to track the bird? It is not always possible to keep the center AF point on the bird at all times. Or is that something that only more advanced bodies do (7D and up)?

Will try on my 600D/T3i as soon as I see a bird flying, or maybe use the dog as an easier test object :-)

Thanks,
Arnt

The 1D IV has an option to choose assist points if you are using just the center AF point. You can choose surrounding points or other variations and it is very accurate. My 1D IV is set all the time in AI, center point with the immediate surrounding points as assist.

The T3i's book says that if the AF selection point is set to automatic, the camera first uses the center AF point to focus. During auto focusing, if the subject moves away from the center AF point, focus tracking continues as long as subject is covered by another point. This would be the mode you would need to be in, AF selection to automatic when in AI Servo Mode.


The T3i does not have any options for assist points that I found, so I am assuming if you want assist points you will have to do as described above.