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A 3-D ("three-dimensional") film or S3D film[1] is a motion picture that enhances the illusion of depth perception. Derived from stereoscopic photography, a special motion picture camera is used to record the images as seen from two perspectives (or computer-generated imagery generates the two perspectives), and special projection hardware and/or eyewear are used to provide the illusion of depth when viewing the film. 3-D films are not limited to feature film theatrical releases; television broadcasts and direct-to-video films have also incorporated similar methods, primarily for marketing purposes.

3-D films have existed in some form since 1890, but were largely relegated to a niche in the motion picture industry because of the costly hardware and processes required to produce and display a 3-D film, and the lack of a standardized format for all segments of the entertainment business. Nonetheless, 3-D films were prominently featured in the 1950s and 1980s in American cinema, and are currently experiencing a worldwide resurgence coinciding with the development of digital media and the introduction of high-definition video standards.
Techniques
Stereoscopic motion pictures can be produced through a variety of different methods. Over the years the popularity of various systems being widely employed in movie theaters has waxed and waned. Though anaglyph (see next section) was sometimes used prior to 1948, during the early "Golden Era" of 3-D cinematography of the 1950s the polarization system was used for every single feature length movie in the United states, and all but one short film[2]. In the 21st century, polarization 3-D systems have continued to dominate the scene, though during the 60s and 70s some classic films which were converted to anaglyph for theaters not equipped for polarization, and were even shown in 3D on TV[3]. In the years following the 90s, some movies were made with short segments in anaglyph 3D. Following are some of the technical details and methodologies employed in some of the more notable 3-D movie systems that have been developed:
Anaglyph

Anaglyph images were the earliest method of presenting theatrical 3-D, and the one 3-D method most commonly associated with stereoscopy by the public at large, mostly because of non theatrical 3D media such as comic books and 3D TV, where polarization doesn't work. They were made popular because of the ease of their production and exhibition. Though the earliest theatrical presentations were done with this system, most 3D movies from the 50s and 80s were originally shown polarized.[4]

In an anaglyph, the two images are superimposed in an additive light setting through two filters, one red and one cyan. In a subtractive light setting, the two images are printed in the same complementary colors on white paper. Glasses with colored filters in each eye separate the appropriate images by canceling the filter color out and rendering the complementary color black.

Anaglyph images are much easier to view than either parallel sighting or crossed eye stereograms, although the latter types offer bright and accurate color rendering, particularly in the red component, which is muted, or desaturated with even the best color anaglyphs. A compensating technique, commonly known as Anachrome, uses a slightly more transparent cyan filter in the patented glasses associated with the technique. Process reconfigures the typical anaglyph image to have less parallax.

An alternative to the usual red and cyan filter system of anaglyph is ColorCode 3-D, a patented anaglyph system which was invented in order to present an anaglyph image in conjunction with the NTSC television standard, in which the red channel is often compromised. ColorCode uses the complementary colors of yellow and dark blue on-screen, and the colors of the glasses' lenses are amber and dark blue.

The anaglyph 3-D system was the earliest system used in theatrical presentations and requires less specialized hardware, but the polarization 3-D system has been the standard for theatrical presentations since it was used for Bwana Devil in 1952[4], though early Imax presentations were done using the eclipse system and in the 60s and 70s classic 3D movies were sometimes converted to anaglyph for special presentations. The polarization system has better color fidelity and less ghosting than the anaglyph system.

In the post-50's era, anaglyph has been used instead of polarization in feature presentations where only part of the movie is in 3D such as in the 3D segment of Freddy's Dead: The Final Nightmare and the 3D segments of Spy Kids 3D.