12/5: Tennis ball being struck

[Undertoad]

From a gallery of high-speed photography, this is what actually happens when a tennis ball is struck: the ball actually compresses to about half its usual size.

To get the image, a flash unit had to be set up with an audio trigger so the photo could be shot via the sound of the racquet hitting the ball. It would seem that setting up the trigger is the key to this sort of high speed photography.

[jet_silver]

A lot of these triggering problems were solved by Harold Edgerton, the E in EG&G for you physical sciences wonks. He developed this kind of stroboscopic photography, among other things.

There is a WGBH portrait of Edgerton that was shown periodically on PBS when I was still watching TV; it may still be making the rounds. Edgerton comes off as very charming and interested in learning how the triggers should work. The 'bat in flight' portrait where the bat is catching a worm is profiled in that show.

The transcript is at http://net.unl.edu/artsFeat/edgertontrans.html

[IndyTone]

Originally posted by Undertoad


From a gallery of high-speed photography...

Any chance you can up the URL of this gallery? It would be keen.

[Undertoad]

Well that would preclude me using another one of the images tomorrow but no biggie:

http://www.pacsci.org/public/educati...nt_photos.html

[russotto]

Originally posted by Undertoad
To get the image, a flash unit had to be set up with an audio trigger so the photo could be shot via the sound of the racquet hitting the ball. It would seem that setting up the trigger is the key to this sort of high speed photography.

The other thing is that you need to do it in darkness. Mechanical clockwork shutters aren't fast enough to capture this sort of thing. So you leave the shutter open and use the flash to get the shot.

An electronic (e.g. LCD) shutter might work nowadays (or might not), but obviously didn't exist when Edgerton worded on this stuff. I believe he invented some of the flash tubes used to do it, also.

[cgifool]

If you're interested in this stuff, I recommend the book Electronic Flash, Strobe by Harold Edgerton. I got mine for just a couple dollars in the cutout bin at Barnes & Noble. He talks all about the circuits and triggering and other fun stuff. If you dont mind paying more, Mit Press has it too.

http://mitpress.mit.edu/catalog/item...ype=2&tid=4740