So this is helpful information, Robin. I would be testing this out if i had a camera in my hands, but I'm currently cameraless.
So the problem I see is that with the majority of portraits, you're going to want a shallow depth of field to accentuate the model/subject. It doesn't seem like using shallow depth of field would ever work with this kind of (focus and recompose) technique. So in those circumstances, would you spend the time to frame the shot and get the focus point over the subject's eye (or other desired location). It seems like this would take too much time in a fast-paced environment (i.e. engagement photos, receptions, candid portraits, etc.). Or maybe you would track the subject with the AF-ON button as you mentioned in that circumstance? But in that case, you'd have to pick the focus point you're using ahead of time, correct?
Robin Casady wrote:
Set camera to AF-C
Custom Menu Settings
a1) Release (camera will take photo whether in focus or not)
a4) AF-ON only (shutter release button does not activate AF)
Center the subject for focusing in the active AF box (I usually use the center).
Activate focus by pressing and releasing the AF-ON button.
Recompose and press shutter release button.
If you want to track a moving subject, simply keep the AF-ON button depressed until you are ready to shoot.
You can use this with your choice of AF boxes and/or AF points.