Our Research Project - Experiment Reports

At The
U.S. Open
(Page 4)

What Made the Camera Special

The digital camera was special because it captured so much more information than regular television video. If you have every looked closely at slow motion replays on television, you know that they are usually blurry when commentators try to freeze the motion. This is because broadcast cameras are no different than the camcorder you family may have at home. Both record only 30 frames a second. When you freeze the action you are actually seeing a still picture of what happened over that 1/30th of a second time span. This is why in high speed activities like sports the pictures look blurred.

Our camera recording at 250 frames a second, was taking 8 times more pictures than this! That gave us much more information for counting spin and doing analysis of the strokes. In addition to the high frame rate, our system also had a high speed shutter. The shutter allowed the camera to freeze the action very clearly in each of the 250 individual frames. In a second, the camera took 250 frames, but the shutter determined how long each picture actually was. What that meant that each of the 250 pictures had a duration equal to the length of the shutter speed. The shutter on our camera went as high as 1/10,000 of a second. For tennis, we determined that 1/2000 was a fast enough speed. That meant that in a second we captured 250 pictures, each of 1/2000 of a second in length. This froze the action so we could see the racket and the ball very clearly, even on 130 MPH serve, like those we would film at the Open.

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