2001: A Space Odyssey
Visual effects

Not one foot of this film was made with computer-generated special effects. Everything you see in this film or saw in this film was done physically or chemically, one way or the other.

2001 contains a famous example of a match cut, a type of cut in which two shots are matched by action or subject matter. After Moonwatcher uses a bone to kill another ape at the watering hole, he throws it triumphantly into the air; as the bone spins in the air, the film cuts to an orbiting satellite, marking the end of the prologue. The match cut draws a connection between the two objects as exemplars of primitive and advanced tools respectively, and demonstrates humanity's technological progress since the time of early hominids.

2001 pioneered the use of front projection with retroreflective matting. Kubrick used the technique to produce the backdrops in the Africa scenes and the scene when astronauts walk on the Moon.

The technique consisted of a separate scenery projector set at a right angle to the camera and a half-silvered mirror placed at an angle in front that reflected the projected image forward in line with the camera lens onto a backdrop of retroreflective material. The reflective directional screen behind the actors could reflect light from the projected image 100 times more efficiently than the foreground subject did. The lighting of the foreground subject had to be balanced with the image from the screen, so that the part of the scenery image that fell on the foreground subject was too faint to show on the finished film. The exception was the eyes of the leopard in the "Dawn of Man" sequence, which glowed due to the projector illumination. Kubrick described this as "a happy accident".

Front projection had been used in smaller settings before 2001, mostly for still photography or television production, using small still images and projectors. The expansive backdrops for the African scenes required a screen 40 feet (12 m) tall and 110 feet (34 m) wide, far larger than had been used before. When the reflective material was applied to the backdrop in 100-foot (30 m) strips, variations at the seams of the strips led to visual artefacts; to solve this, the crew tore the material into smaller chunks and applied them in a random "camouflage" pattern on the backdrop. The existing projectors using 4-by-5-inch (10 cm × 13 cm) transparencies resulted in grainy images when projected that large, so the crew worked with MGM's special-effects supervisor Tom Howard to build a custom projector using 8-by-10-inch (20 cm × 25 cm) transparencies, which required the largest water-cooled arc lamp available. The technique was used widely in the film industry thereafter until it was replaced by blue/green screen systems in the 1990s.
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