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04-08-2010, 10:19 AM   #16
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This may be the case. Looking at the shot. The background is in focus. The focus point is here:
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It is very possible that the light behind overpowered the AF. It is also possible that you locked focus behind them and with some camera movement, recomposed the shot. But the background is sharp in the shot, to the AF locked on behind them.

04-08-2010, 07:31 PM   #17
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QuoteOriginally posted by BethC Quote
also, normally I use center focus, focus on eyes, lock it and then recompose...Is that not the best method when shooting a large number of people?
I'd say no. Large number of people means no one person takes up the whole frame, and that means any single person's head is *much* smaller than the AF sensor. Meaning if you point at a head, you are *guaranteed* the background will alo be in range of the focus sensor, and it's then a crapshoot as to which the camera chooses. You're better off aiming for the midriff. Aiming for the eyes makes sense in a tight shot of a single face, not so much for groups or any shot where the face does not dominate the shot.
04-09-2010, 07:02 AM   #18
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QuoteOriginally posted by Marc Sabatella Quote
... any single person's head is *much* smaller than the AF sensor. Meaning if you point at a head, you are *guaranteed* the background will alo be in range of the focus sensor, and it's then a crapshoot as to which the camera chooses.
I bet that's what happened in this situation; the AF sensor did see the eyes (while focusing, i.e., before recomposing -> Peter, I believe your "X" does not mark the position of the AF point when the focusing occurred) but also the high contrast background and the latter won.

This is an issue of the camera's AF system, not one of the lens. It will happen with all lenses in a similar situation. Very rarely do lens specifics really influence the AF, it is primarily the camera's AF system which does the job.

Last edited by Class A; 04-09-2010 at 07:07 AM.
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