Quote Originally Posted by 2F/2F View Post
I view D of F as the area which for ones intents and purposes appears as sharp as the plane of critical focus, not simply as the area which appears acceptably sharp. To use your term: the "acceptable unsharpness" matches between the plane of focus and the areas that simply appear sharp.
Now here's a rare opportunity to reply to something, saying that it is just semantics, and be correct (and not in disagreement, by the way).