This is not a question about when. This is a question about how.
AF works by an AF sensor that detects where focus should be. What happens after this? Does it tell the lens/camera screw how far to turn, and assume itís OK? Or does it say move this direction, and keep checking/moving until it finds good focus?
Iím trying to understand why a lens thatís fine with MF can be off in AF. Does accuracy depend on whether the lens is screw focus, motor focus, or USM focus?
Also, how do you MF quickly? On a crop body, it takes me 1-2s to find the sharpest point. This makes me useless trying to MF people at an event.