3-D Television:
an Overview

Since the beginning of television there has been the dream of broadcast in three-dimentions. There is an irony in that the 3-D movie craze of the 1950's was driven, at least in part, by the Hollywood's need to win back the audience lost to the new upstart television. Proponents of 3-D TV are fond of pointing out how first color then stereophonic sound have become normal, accepted parts of the viewing and listening experience. By extension, we are supposed to believe that 3-D will soon become part of TV. It is always coming soon, just over the horizon or possible and pr actical now if people would just purchase and wear some new gadget.

After 20 years of working with almost every method of 3-D imaging my sense is that 3-D will not and need not become universal, mainstream or even simple. It is a very special form of imaging and it will always be a special option with every medium. What is important is that when it is done it is done well.

Let's start by looking at what 3-D is and isn't. The world out there exists in at least three dimensions: height width and DEPTH. We (humans) visually perceive the world in depth by a variety of means. One of these means is Stereoscopic or binocular vision in which the brain analyzes the difference between what the two eyes see. This is not the only or even the dominant way that we experience depth but it can be the amazing. For the purposes of our discussion, 3-D Television is any method of viewing where two different images are presented to each of the viewer's eyes making stereoscopic vision possible. All 2-D media from drawing to photography to film to television have ways of conveying depth but binocular, stereoscopic imagery really is something else and that is really what we mean when we say 3-D. There is one popular and important thing that is called 3-D but isn't 3-D in our sense. When a computer is used to render a flat 2-D image based on three dimensions of information it has stored about a scene, that is also called 3-D Graphics although it is rare that the computer is asked to render stereoscopic pairs of images.


It is over one hundred years since Louis DuCos du Hauron proposed that the two images needed for 3-D be presented in two complementary colors and the viewing public be given spectacles of those two opposite colors for viewing. One of the two colors is red and the other color is either green or a blue-green mix. This anaglyph process can work well for printing on paper or photographic film and works great on a RGB computer screen but, unfortunately, it generally fails the test of our NTSC color system.

Over & Under and Side by Side

Clever inventors have come up with every possible combination of putting the two images next to each other or above each other or opposite and then viewing the pair with the aid of lenses, mirrors, prisms and the like. Often one of these arrangements will be perfect for one specific application. (ie. a 3-D arcade game)

Alternating shutter

One of the earliest methods of viewing 3-D with moving images has been to alternate left & right images rapidly and to provide the viewer with glasses that alternately shutter so that each eye gets the correct image only. In the 1920's the shutter was a rotating disk mounted in front of each seat in the movie theater. The idea did not catch on. Recent developments in the area of liquid crystals have made possible lightweight electronic shutter glasses and some promising work is starting to be seen. It is useful to divide liquid crystal shutter systems into two groups: high-speed or double frame rate and field-sequential. The high-speed or double frame rate systems alternate the left & right images very rapidly and the the resulting 3-D can look great. The disadvantage of this system is that the electronics and monitors are non-standard; meaning expensive. The field- sequential systems alternate left & right views in the two fields that make up our standard interlaced television system. This makes this system eminently practical but the reader will need to judge for him/her self whether the amount of flicker is acceptable.


In 1922, a German physicist named Carl Pulfrich discovered that if an object moves horizontally across your field of view while you have a dark filter over one eye, the object will be seen as forward or back in depth depending on the speed and direction of the object. The reason for this is a time delay for the eye wearing the filter. It is not known whether Pulfrich had any idea that his discovery would lead to a method of 3-D television. In the late 1960šs a device called "TV Stereo Spex" was widely sold that claimed to offer 3-D from your existing TV. The device enabled you to darken one of your eyes by rotating one of two polarizing filters. It also had blue and yellow filters to heighten the effect. Inspired by this device, a number of filmmakers produced films that exploited this effect. I started using the Pulfrich effect in 1975 and have developed my own proprietary incarnation of the process, PullTime 3-D. Designing for this process is a tricky choreography job since direction and speed of movement is almost the sole determinant of depth. Still, for the right subject matter (ie. music video) it is possible to create 3-D television that is 100% compatible with all normal TV and does not distort color in any way. At this point, aprox. 20,000,000 of my PullTime 3-D glasses have been distributed.

3-D Without Glasses

Obviously, it would be wonderful to have 3-D television that does not require any kind of 3-D glasses or special viewing device. Some very interesting research is being done, but, don't hold your breath. The MIT MediaLab has created prototype holographic television. Japanese researchers have created 3-D TV without glasses using a barrier strip in front of a flat screen HDTV display. It looks great until you move your head. A couple of American groups have developed systems that insert subtile or not-so-subtile movement into what can become a conventional TV image with the claim that this makes the picture more 3-D.

Polarized Projection

When 3-D movies are projected in a theater, two strips of film are projected, in sync, through two polarizing filters that are aligned at right angles to each other. The audience wears corresponding polarizing glasses. The same thing can be done with video projection although the lower brightness of video projectors this less desirable.

Gerald Marks 1995

American Cinematographer Video Manual

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