Front projection effect
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A front projection effect is an in-camera visual effects process in film production for combining foreground performance with pre-filmed background footage.
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[edit] Working
In contrast to rear projection, in front projection the background image is projected on to both the performer and the background screen. This is achieved by having a screen made of Scotchlite, a product of the 3M company that is also used to make screens for movie theatres. Scotchlite is made from millions of glass beads cut in half and affixed to the surface of the cloth. These glass beads reflect light back only in the direction in which it came, far more efficiently than any common surface. In fact, Scotchlite is 1000 times more reflective than the human body.
The actor (or horse or spaceship, etc.) performs in front of the reflective screen with a movie camera pointing straight at him. In front of the camera is a one-way mirror angled at 45 degrees. At 90 degrees to the camera is a projector which casts a faint image of the background on to the one-way mirror which reflects the image onto the performer and the screen; the image is too faint to appear on the actor but shows up clearly on the screen. In this way, the actor becomes his own matte. The combined image is transmitted through the one-way mirror and recorded by the camera.
Front projection was invented by William F. Jenkins, better known to readers of science fiction by his nom de plume as Murray Leinster.
The technology needed for front projection was available since the invention of Scotchlite in the 1940s, but apart from some minor technical experiments in 1949, the process would not be used for feature films until 1966, during the filming of 2001: A Space Odyssey. The actors in ape suits were filmed on a stage at Elstree and combined with footage of Africa. (The effect is revealed in the glowing cheetah's eyes reflecting back the light.) Dennis Muren utilized a very similar solution for his 1967 debut film Equinox, although Muren's technique didn't employ Scotchlite. Two British films released in 1969, On Her Majesty's Secret Service and The Assassination Bureau, used the technique.
[edit] Zoptics
Front projection was chosen as the main method for shooting Christopher Reeve's flying scenes in Superman. However, they still faced the problem of having Reeve actually fly in front of the camera. Yugoslav effects wizard Zoran Perisic devised a new refinement to front projection that involved placing a zoom lens on both the movie camera and the projector. These zoom lenses were synched by computer so as the camera zooms in, the projector zooms out, or vice versa. The background grows smaller and the actor grows bigger; thus Superman flies towards the camera. Perisic called this technique Zoptics. The process was also used in two of the Superman sequels — but not used in the fourth due to budget constraints — Santa Claus: The Movie and Perisic's sole film as director, Sky Bandits (also known as Gunbus.)
[edit] IntroVision
In Front projection, light from the projector that travels through the one-way mirror is “soaked up” by black velvet. In IntroVision, the black velvet is replaced by another Scotchlite screen that reflects the image back towards another Scotchlight screen placed before the performer. Thus, the same image appears from two different sources and lands on two different screens creating a “3D” effect[citation needed]. IntroVision was first used in Outland to combine star Sean Connery with models of the Io mining colony. It was also used in Under Siege, Army of Darkness and The Fugitive, where it seemed to place Harrison Ford on top of a model bus that was then rammed by a model train.
[edit] Front projection phased out
Front projection had several advantages over its main rival bluescreen. It didn't have the thick black outlines that sometimes appear on bluescreen films. It was less time consuming - and therefore less expensive - than the long process of optically separating and combining the background and foreground images using an optical printer. It allowed the director (if not necessarily the actors) to see the background and call out necessary adjustments (“Jump now, Harrison!”). And, especially with Zoptics, it was a more flexible system that allowed for more complex sequences that could be attempted at the time with bluescreen. However, advancements in digital compositing have rendered front projection obsolete. The last major blockbuster to extensively use front projection was the Sylvester Stallone action thriller Cliffhanger from 1993.
