WOW, this is really helpful. Thank you so much.

This is exactly what I want to know.

Most of the time, when I pretty close to the object, I used to use the manual focus, by guess the distance. Auto focus, in such circustance, somehow, may focus on somewhere out of my object. As a result, I lost the critical moment, maybe. If I have enough time in most of the condition, I'll prefer to have auto focus, but aim on specific point.

This is why I worry about those focus function.

Thank you very much.