Will 3-D TV be a Winning Technology?

Buried at the end of Section B (Marketplace) in today's issue of  The Wall Street Journal was a one-sixth-page article (blown up to nearly a half page by an enormous photo of a pretty Japanese lady wearing the modern version of 3-D glasses) discussing the the hurdles 3-D television faces to becoming a commercial success. According to the article, television manufacturers in Korea and Japan (specifically, Samsung Electronics, LG Electronics, Sony, and Panasonic) "... see 3-D as the next big technological breakthrough...." The article intimates that the technology's biggest hurdle is getting consumers to upgrade so soon after paying up for the transition to HDTV.

It fails to mention the possibility that the technology might turn out to be as useless for television as the proverbial enhanced mammary glands on a male Bos taurus.

True 3-D visual experience relies on solving the technical problem of presenting separate images to the viewer's left and right eyes. The two images must differ slightly to allow the viewer to subconciously solve the parallax problem locating the objects in the scene relative to the presumed camera position along the third spatial dimension (range).

An elegant technical solution became commercially available a couple of decades ago, when electron-microscope maker Cambridge Instrument Company introduced a scanning electron microscope (SEM) featuring a display system using circular polarization. Images for one eye were displayed using light with left-handed circular polarization while images for the other eye used right-handed circularly polarized light. The viewer wore glasses with circularly polarized lenses. The lenses on one side passed left-handed light, while the other passed right-handed light. Circular polarization has two advantages as a coding scheme:

• polarization is, in general, color neutral, so full-color images can be displayed;
• circular polarization is maintained during reflection and transmission of light, so the system is harder to accidentally spoof.

So, while the technical challenge is pretty much a thing of the past, there's a big issue with utility. You see, parallax is not the only way to signal range information. More importantly, parallax only works at short distances.

Because human eyes are necessarily spaced only a few inches apart (baseline). Other creatures may enhance parallax perception by mounting their eyes on stalks protruding from the sides of their heads, but humans obviously don't. This limited eye separation combines with the eye's finite angular resolution to restrict the effectiveness of parallax as a range cue to distances smaller than the order of 100 feet. In fact, other means of judging distance become more important at ranges beyond a few tens of feet.

Leonardo Da Vinci pointed out the importance of creating a 3D illusion by depicting distant objects as seen through an intervening mist. While he noticed the related illusion that objects appear magnified when seen through a fog, he missed (no pun intended) the explanation that the fog causes the brain to overestimate the distance to the object. It then solves the resulting cognitive dissonance by percieving a larger object located at the overestimated distance.

Walt Disney solved the problem of portraying distance on a flat screen in his 1942 film Bambi (not to be confused with Marv Newland's 1969 Bambi Meets Godzilla, which I couldn't resist linking to) by the simple expedient of introducing parallax while moving the assumed camera's point of view. He showed nearer objects moving more as the camera dollyed (moved along a track at right angles to the line of sight) than more distant objects.

Both solutions arise naturally in live-action video. These solutions become even more powerful when combined with the immersive experience of wide-screen HDTV.

So, adding parallax through circularly polarized stereoscopic projection gives a realistic 3D effect only for objects that are a few tens of feet from the camera. Anything farther away, and other range cues are far more important.

I haven't done the study, and I don't know if anyone else has, but it would be interesting to know what percentage of scenes in motion pictures or TV mainly include objects less than, say, 30 feet from the camera.

Photographers making images for the stereoscopic viewers popular in the late 19th Century were fond of creating cityscape views with points of view separated along a baseline many times that of human eyes. Nobody would percieve parallax when visiting the actual scene. All they really accomplished was to make the scene look like a miniature model, reduced in scale by a factor equal to the ratio of the camera baseline to the distance between the viewer's eyes!

Trying to enhance the stereo effect of video content by recording with an overly long baseline will have the same effect for TV. You'd make Jaws look like a 3 foot sand shark. The Grand Canyon would look like a drainage ditch.

In the final analysis, how much extra would you pay for 3D TV? How much would it enhance your enjoyment of sports, for example? If your sport is chess, it might do a lot. If your sport is, say, football, or baseball, or motor racing, or sail boating, on the other hand, not so much.

Whether 3D TV will be a commercial success in the long run has nothing to do with market-introduction timing, or whether folks have already gone through a recent upgrade to HDTV. It's about whether the marginal enhancement of their viewing experience is enough to make folks give a rotten dingo's kidney about it.