stereoscopy is the illusion of three dimensional experienced by the viewer due to various optical perceptions. This is done by using technology that plays off of the optic channels within our brains. Some of the ways in which this is done are:

Occulation of one object by another
Substended visual angles of a corresponding object of understood size
Linear perspective which is the convergence of edges made to be parallel
Vertical positioning placing some objects higher in the scene to indicate that they are further away
Instituting effects such as haze, desaturation, and shifting the blushness
Changing the size of textured pattern details

The above optical viewing perspectives are all found in traditional two dimensional representations of reality including photos, television, paintings, and film. Stereoscopy involves the enhancement of these features to illustrate more clearly through dual perspective the depth within the image, frame, or video. This can be provided by supplying each eye with a different image simulating the optical difference required to create the 3d effect.
Stereopsis is the technical term for the spit of an image with slight variation between the two images to manipulate the visual perception to include the depth. The variation is called retinal, binocular, or horizontal disparity. Naturally this occurs in human sight due to the difference in eye position on the human body. This does not create depth perception it mimics and illustrates it.

Developed in the 1830’s by Sir Charles Wheatstone stereoscopic 3D was the first of the many varieties of 3 dimensional technology today. Stereoscopic 3D or binocular vision is that which provides a different 2D image to the right eye than the left eye. Through this process the viewer has the illusion of depth because the two offset images when combined within the brain create a perspective of three dimensions. Commonly the viewer must wear special eye glasses that combine the offset images after the light moves through the filtered glasses. Although this is done through various types of eyeglasses the most commonly recognized style is the red and cyan glasses. Many other types have been used as well. The active forms are the Liquid crystal shutter glasses and the “red eye” shutterglasses. The passive types are linearly polarized glasses, circularly polarized glasses, infitec glasses and inficolor 3d glasses.

Autostereoscopic 3d technology is currently a limited view 3d system in which the user must maintain a certain viewing position to attain the three dimensional effect rather than wearing eye glasses. Recent advancements will prove that glasses free 3D with free range viewing angles are becoming a reality. The viewing optics provide a split image directionally for the viewers eyes. Providing various views of the same scene. Automultiscopic display modality provide more than just two views allowing the viewer to move left and right to various degrees and still maintain the correct 3d view. This would include technologies such as parallax barriers and specular holography.

Computer-generated holography
This form of 3d technology is still not beyond the laboratory stage for all intensive purposes. It creates a field of light which is nearly identical to that which would be absorbed by eyes at the original scene both vertical and horizontally within the parallax of viewing range and angles. Quite possibly computer-generated holography is the most convincing of all of the 3d technologies. Technology is currently in pre introductory stages by Sony and other firms. Providing full 360 degree viewable space this mode of display will be the preferred method for many uses including military in a few short years.

Volumetric displays
Volumetric 3d displays work in unison with a tangible mechanism displaying points of light within a volume. These displays utilize voxels rather than the customary pixels. Other modes have been developed to achieve the same basic point. One such method is the use of an infrared laser to focus on a point in space creating a plasma bubble which emits visible light.

Holographic Display
The 3d holographic and electro holographic displays are most likely the future of 3d. Having the ability to reconstruct 3d images, stills, and videos at full parallax. Parallax being defined as immediate objects moving across the screen as distant objects move more slowly representing reality of perception and depth. Holographic 3d does not use any form of eyeglasses and create zero visual fatigue for the viewer.

Problems with 3D technology
Every current 3d technology contains a flaw or limitation whether it be range of visibility, masses of equipment, or insurmountable cost. To this day there are no outlines how things should be done such as the standards of multi-camera filming, placement, post production processing as there has been established for two-dimensional filming.

How does native 3D compare to Converted 3D?
While Native 3D video capturing has the visual benefit of being able to capture infinite layers and contours it only provides a slight benefit to the viewer. Aesthetically it is nearly identical. A  sommelier of wine is an individual with an uncanny pallet for the hidden undertones of a wine. Similar to 3D in the sense that only an expert would truly experience a difference.