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Tools - Video Cameras

 

Using Video Cameras for High-Speed Photography

colered4.jpg (11819 bytes)

Is it possible to use a video camera for high-speed photography? The answer is definitely yes, assuming you're using a CCD chip camera. (Almost everyone does nowadays.) Of course, the result is not what you'd get from a camera designed for filming high-speed motion.  With a consumer-grade camera, any high-speed event that you film will appear on just a single frame of the film.  The image above is such a frame. You can't get a sequence of adjacent frames of the same event, because the film only runs at 30 frames per second. If, however, you're willing to spend some time and invest some money in video-editing equipment and computer hardware/software, it's possible to create animations of high-speed events using a series of frames from videotape. Basically, this is a high tech version of the flip book. The animated gif of a splashing milk drop below was produced using such techniques.

 

Small animated splashEach frame of the animation is an image of a different drop. The drops fell from a funnel at a rate of about 3 per second. Each drop passed through a photogate, which triggered a delay timer. After a given time delay, the flash discharged. If the delay were constant, each drop would appear in the same place and would thus seem to be levitating. In order to give the illusion that a single drop was falling in slow motion, the time delay was advanced gradually during filming. The video clip was then digitized and individual frames were exported as bitmapped files. Finally, the series of files was assembled into a gif animation. A clue that each image is of a different drop is the jitter in the droplets of the crown. Click on the animated gif for a larger version. 

 

Follow the Video links for information on capturing high-speed events on videotape and on creating animations.  Then check out the Snapped Towel project in the Projects section for an example of the use of video in measuring very high speeds.

 

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