The process of making and presenting images using ‘left eye’ and ‘right eye’ cameras. The resulting ‘left eye’ and ‘right eye’ stereo images allow audiences to perceive depth into and out of the screen. Although the technique can add greatly to the viewing experience and is often referred to as ‘3D’, viewers cannot look around objects – as would be the case with real 3D. Stereo television and film can create a 3D illusion, but it not real 3D.


In stereoscopy, presenting objects from the left and right eyes’ point of view in the same way that our eyes would look at them in the real world, creates the depth effect. If the left and right eye images of an object are coincident at the screen, then it appears to be at the distance of the screen. If the left and right images on the screen are crossed over, with the right image on the left and the left image on the right, then the object appears to be in front of the screen as our eyes converge on the images. If the left and right images are not crossed over but closer together than the distance between our eyes (interocular distance generally taken as 63.5 mm for the average adult), then the object appears to be behind the screen as our eyes converge less. To show an object at infinity left and right images are shown spaced by the interocular distance.

HD video and DCI digital movies sparked development in new shooting technologies that can make live 3D TV. But generally post production is needed to correct unwanted differences between left and right cameras, and to finesse the point of view and perspective. Exhibition become far easier with digital cinema were one projector can sequence left and right images replayed from one player. This removes the nightmare of aligning and keeping two projectors, and running two films in sync and registration; even then weave, scratches and sparkles can lower the quality of presentation. Now most cinemas are 3D-capable and have a viewing system to sequence the left and right images into images into the correct eyes – such as Real D, Dolby or McNaughton. These require wearing glasses that are passive polarized (Real D), passive frequency based (Dolby) or active switched (McNaughton). Live shooting and easy exhibition means that live events can be shown on cinema screens – giving audiences a new experience and theaters a potential new revenue stream.

For television, 3D screens and viewing systems have been developed but usually require viewers to wear 3D glasses (active or passive depending on the system) to sequence the left and right images to the correct eyes. Probably the greatest domestic application has been for use in the virtual world of computer games.

See also: 3D

Websites: Dolby