At The USTA Training Center (Page 16)

The value of teamwork in creating experimental scripts is demonstrated by one of the suggestions made by Howard Brody of the USTA Sports Science Committee. How did we know for sure, he asked, that the camera was really filming at 250 frames per second? For example, if the frame rate were off by even 25 frames per second, that would introduce an automatic 10% error into all our measurements, a potential error that the team would not be aware of!

The team decided to test the frame rate by filming the second hand on John's watch. After filming several seconds of the movement of the second hand, John patiently counted the frames while viewing the video. Using the camera's remote control, he advanced the tape frame by frame as the second hand moved. The result? Ten different counting tests all yielded between 248 and 250 frames per second. It was hard to say which may have been more accurate, John's watch or the camera! In any case, thanks to Prof. Brody, the team was sure that the camera's frame rate was extremely accurate and could be trusted as a basis for doing the data capture and analysis