Animation is the technique in which each frame of a film is produced individually, whether generated as a computer graphic, or by photographing a drawn image, or by repeatedly making small changes to a model unit (see claymation and stop motion), and then photographing the result with a special animation camera. When the frames are strung together and the resulting film is viewed at a speed of 16 or more frames per second, there is an illusion of continuous movement (due to the persistence of vision). Generating such a film is very labour intensive and tedious, though the development of computer animation has greatly sped up the process.
File formats like GIF, QuickTime, Shockwave and Flash allow animation to be viewed on a computer or over the Internet.
Because animation is very time-consuming and often very expensive to produce, the majority of animation for TV and movies comes from professional animation studios. However, the field of independent animation has existed at least since the 1950s, with animation being produced by independent studios (and sometimes by a single person). Several independent animation producers have gone on to enter the professional animation industry.
Limited animation is a way of increasing production and decreasing costs of animation by using "short cuts" in the animation process. This method was pioneered by UPA and popularized by Hanna-Barbera, and adapted by other studios as cartoons moved from movie theaters to television.
Although most animation studios are now using digital technologies in their productions, there is a specific style of animation that depends on film. Cameraless animation, made famous by moviemakers like Norman McLaren, Len Lye and Stan Brakhage, is painted and drawn directly onto pieces of film, and then run through a projector.