3-4 milliseconds...

[gzhpcu]

The ball is on the racket only about 3-4 milliseconds. The parameters relevant to the flight of the ball I would think are:

1) trajectory of incoming ball

2) spin of the incoming ball

3) inital point of impact by the racket on the ball (related to 4) and 7)...). If you divide the face of the incoming ball in quadrants, the initial impact point will vary based on the type of shot.

4) angle of the racket face at impact

5) the point on the racket where initial impact occurs (sweet spot, off center, etc.)

6) the racket characteristics (flexibility, etc.)

7) force vector (strength, direction) applied by racket face to the ball at impact

8) ball characteristics affecting deformity

Federer, for example, has a slight tilt and off center hit here:
Federer forehand

Am I forgetting something?

Anyway, it seems intriguing that, for example, in the case of a forehand, very intricate biomechanical pre- and post-movements are needed to for a brief 3-4 millisecond impact. A windshield wiper finish adds topspin even though the up and down movements occur way after impact. All this to only set 4) and 7) efficiently.

[maverick1]

Great video of federer.

I am guessing it is 1000 fields (500 frames) per sec. When you step thru it, you see genuine motion in every other step. In between, it is just some video artifacts adjusting.

I can't add anything that you don't know, but I don't see a mystery.

Federer's racket IS moving upwards through contact, hence the topspin. When you step through the frames during contact, you see the racket move vertically during these frames. It is a little slower than after contact, but that is probably because the impact slows the racket briefly.

Also, 4 ms is not an insignifcant time interval. From the serve videos, It seems the pros pronate about 10 degrees in 4 millsec. In the regular speed(30 fps) videos, it is typical to see the racket go from horizontal to vertical in the last frame before contact occurs

[gzhpcu]

What seems mysterious to me is all of the biomechanical movement pre- and post-impact to determine a 3-4 millisecond impact.