Our eye is an excellent optical and imaging system, but requires a microscope
when we look at small objects. Similarly, when we watch fast events, we can't
catch an instant without a suitable tool.

　Do you have a way to watch the instant ? 
Yes, we have a good method.

　This method is called the high speed photography , or high speed video movie.
Recently it may be called as the high speed imaging.

　In general, the high speed photography has two meanings. One is a slow
motion movie using high speed motion picture cameras or high speed video
cameras, and the other is a single photograph or frozen image using a short
flashlight. It may be defined that the former is motion pictures of multi frozen
images, and the latter a single frozen picture.

　 First, I explain about the high speed motion pictures.
The principle of high speed motion pictures is that we record many continuous
pictures in a short time, then playback them in a long time. By changing the
ratio of pictures in unit time, we can watch fast events which motions are
slowed down. The time in a fast event is expanded, so it is called as the time
microscope.

　For more detailed explanation.

　If the pictures are playbacked on a screen at rate of one picture per second
(PPS), we can watch them as an each separate picture. However if pictures are
playbacked at over 16 PPS, we can't recognize them as an separate one from the
afterimage effect of our eyes. Movie uses the afterimage effect of our eyes.
Though a recent movie film may run at 30 PPS ( video camera runs also at 30
PPS ), the traditional movie film runs at 24 PPS in cameras, then it is
playbacked at the same rate in film or video projector. So the motion speed
becomes same and natural. If the film runs at 240 PPS in camera, and at 24 PPS
in film projector, the motion speed does not become same, but ten times slower
than the natural speed of the event. In case of video camera, the motion
becomes also ten times slower if you use your camera at 300 PPS. So we can
watch fast events by expanding the time. It is a trick of slow motion movie.

　As these devices, there are several kinds of high speed camera. They have
different optical, mechanical and electrical imaging systems. You can choose
your better one from various cameras to meet your specific needs depending on
the characteristic of events.