Originally Posted by sureshs
I have heard around 10 degrees. How do you reconcile that with your pics below? Is it that the racket face (in these cases) changes from vertical to slightly closed over the dwell time? Or the photos below are slightly before contact?
You can't tell because the view is from the back. And the height of the camera affects the perceived racket face angle as well. You don't need a physics degree to know that. There is no way to know. Has nothing to do with dwell time.