3-D technology...

3-D also called  stereoscopic

3-D improve the illusion of reality in motion pictures has been stereoscopic, or three-dimensional, cinematography. 

“3-D” films use two cameras or one camera with two lenses. The centres of the lenses are spaced 2 1/2 to 2 3/4 inches apart to replicate the displacement between a viewer's left and right eyes. Each lens records a slightly different view corresponding to the different view each eye sees in normal vision.

Motion-picture process that gives a three-dimensional quality to film images. It is based on the fact that humans perceive depth by viewing with both eyes. In the 3-D process, two cameras or a twin-lensed camera are used for filming, one representing the left eye and the other the right. The two lenses are spaced about 2 1/2 inches (6.3 cm) apart, the same as the separation between a person's eyes. The resulting images are simultaneously projected onto the screen by two synchronized projectors. The viewer must wear differently tinted or polarized glasses so that the left- and right-eye images are visible only to the eye for which they are intended. The viewer actually sees the images separately but perceives them in three dimensions because, for all practical purposes, the two slightly different images are fused together instantly by his mind.

Studios and independent producers experimented with 3-D throughout the 1920s and '30s. Many of the technical problems were later solved by the Natural Vision process, which used striated polarized lenses (with similarly striated viewing glasses for the audience) that made it possible to film in natural colour and correctly applied the convergence principle of the human eye in the filming. The first 3-D film in Natural Vision was Bwana Devil (1952), which was followed by several hastily shot action films. It is generally believed that the popularity of 3-D in the United States subsided after about a year because of the low quality of the films presented. Filmmakers in Italy, Germany, The Netherlands, Great Britain, and other countries experimented with 3-D at about the same time as did those in the United States, but its popularity in Europe soon faded when the illusion of depth was no longer a novelty. The process experienced a minor revival beginning in the 1970s.


The Polaroid system, used for commercial 3-D movies since the early 1950s, is based on a light-polarizing material developed by the American inventor Edwin H. Land in 1932. In this method, known as Natural Vision, two films are recorded with lenses that polarize light at different angles. The lenses on the glasses worn by spectators are similarly polarized so that each admits its corresponding view and blocks the other. Early versions of Polaroid 3-D used two interlocked projectors to synchronize the two pictures. A later system, revived in the 1970s and 1980s, stacked the left and right components vertically on half-frames two sprocket holes high. The images were converged by means of a mirror and/or prism.. 

Despite many efforts to create “3-D without glasses” (notably in the U.S.S.R., where a screen of vertical slats was used for many years), audience members have had to wear one of two types of special glasses to watch 3-D films. In the early anaglyph system, one lens of the glasses was red and the other green (later blue). The picture on the screen viewed without glasses appeared as two slightly displaced images, one with red lines, the other with green. Each lens of the glasses darkened its opposite colour so that each eye would see only the image intended for it... 

Stereoscopy

Science and technology dealing with two-dimensional drawings or photographs that when viewed by both eyes appear to exist in three dimensions in space. A popular term for stereoscopy is 3-D. 

Stereoscopic pictures are produced in pairs, the members of a pair showing the same scene or object from slightly different angles that correspond to the angles of vision of the two eyes of a person looking at the object itself. Stereoscopy is possible only because of binocular vision, which requires that the left-eye view and the right-eye view of an object be perceived from different angles. In the brain the separate perceptions of the eyes are combined and interpreted in terms of depth, of different distances to points and objects seen. Stereoscopic pictures are viewed by some means that presents the right-eye image to the right eye and the left-eye image to the left. An experienced observer of stereopairs may be able to achieve the proper focus and convergence without special viewing equipment (e.g., a stereoscope); ordinarily, however, some device is used that allows each eye to see only the appropriate picture of the pair. To produce a three-dimensional effect in motion pictures (see 3-D), various systems have been employed, all involving simultaneous projection on the screen of left- and right-eye images distinguished by, for example, different colour or polarization and the use by the audience of binocular viewing filters to perceive the images properly. In holography the two eyes see two reconstructed images (light-interference patterns) as if viewing the imaged object normally, at slightly different angles...