I use Canon SLRs. When using live view focusing, there is a rectangle which turns green when the focus is achieved.

My question is: Is there a single focus point at the center of the rectangle? Or does the camera use the edges of the rectangle or how does it work?

I need to focus more precisely in live view for some of my shots and knowing how this works would be very useful. Thanks.

I use Canon SLRs. When using live view focusing, there is a rectangle which turns green when the focus is achieved.

My question is: Is there a single focus point at the center of the rectangle? Or does the camera use the edges of the rectangle or how does it work?

I need to focus more precisely in live view for some of my shots and knowing how this works would be very useful.