Twenty-four
frames per second is a fixed, unchanging constant in the USA for
motion picture film. One second of real time = 24 frames per second,
or 24 FPS. This holds true for all standard professional film
formats in the U.S. (with the exception of videotape at 29.97
a.k.a. 30 FPS) including 16mm and 35mm film.
The
pre-sound format was at 18 FPS. The reason for this was this;
before synchronized sound was developed for motion pictures, 18
frames per second was the least number of frames per second that
could create the illusion of the motion picture without looking
too jittery. Many frames per second change into hundreds of feet
of film very quickly, so keeping the frames per second count to
the lowest possible number was critical for the commercial success
of the infant motion picture industry. With the development of
synchronized sound, it was found that the resolution of the lip
movements of the actors was too coarse to support the sound of
the recorded voice. At 18 FPS, speech looked like a Godzilla movie
poorly dubbed into English. After some experimentation, it was
determined that 24 frames per second was the least possible number
and the most economical means of maintaining the illusion of the
synchronized sound motion picture and kept the business profitable
and an ongoing industry today. The European standard is 25 frames
per second, just like their PAL video standard.
