Add exclude center to autofocus (in same pane as "crop auto focus frame")

I used my AT66ED w/WO.8 FF/FR and I think it was 15% edge exclusion. Focus did not turn out well at all. The farther from the center the softer the focus was. I got rid of the exclusion and did much better, but not perfect. I'd love to see a subframe for focus as Jared mentioned. I think a crop of the middle third between center and edge would be just the ticket.

Mark