Motion picture images are presented to an audience at a constant speed. In the theater it is 24 frames per second, in NTSC (US) Television it is 30 frames per second (29.97 to be exact), in PAL (Europe) television it is 25 frames per second. This speed of presentation does not vary.
However, by varying the speed at which the image is captured, various effects can be created knowing that the faster or slower recorded image will be played at a constant speed.
For instance, time-lapse photography is created by exposing an image at an extremely slow rate. If a cinematographer sets a camera to expose one frame every minute for four hours, and then that footage is projected at 24 frames per second, a four-hour event will take 10 seconds to present, and one can present the events of a whole day (24 hours) in just one minute.
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