How 3-D TV looks -- and works

LAS VEGAS -- After spending most of yesterday hearing about 3-D TV, I got to spend a little time watching it this morning at a small theater set up in Panasonic's booth.

The highlight reel in question had the usual bits -- sports, nature, travel and, of course, a clip from "Avatar" -- and it was interesting to see how these various types of video showed up in 3-D. (The presenter also briefly put some 3-D footage of the audience on the screen, using the camera you see below.) There wasn't much depth of field to be perceived in shots from the top of a football or soccer stadium, while foreground elements such as fish swimming around a coral reef, falling confetti or powdery snow tossed up by a downhill skier seemed to float in front of the screen.

Also interesting: The first pair of glasses I tried didn't quite work. I was seeing slightly double, which should happen only when you're not wearing 3-D glasses. Panasonic chief technology officer Eisuke Tsuyuzaki suggested that was a symptom of the battery in the glasses running low.

Battery? Yes. The glasses you'll use to watch 3-D TV aren't like the paper ones used in older 3-D productions or even the plastic ones I wore to watch "Avatar" last month. Each lens is actually a powered LCD that acts as a shutter, turning opaque and then clear again 60 times a second -- first the left lens, then the right lens. A wireless transmitter in the glasses in turn ensures that this on/off shutter action stays in time with the 3-D screen's 120 times-per-second refresh rate; your brain then combines the two images into a (theoretically) seamless whole.

Tsuyuzaki provided some other technical details about how 3-D TV can work. It turns out that this technology is an effective use for all the storage capacity of a Blu-ray disc; although you don't need a separate copy of the movie for each eye, the added data does make the resulting file from 130 to 140 percent the size of a 2-D title. That, he added, should still leave room for the traditional movie extras -- and if you play a 3-D Blu-ray disc on a 2-D player, you'll get the normal, 2-D version of the movie.

That backwards compatibility does not apply to DirecTV's upcoming 3-D channels, though: If you, for some reason, sign up for them but forget to buy a 3-D TV, you'll see everything slightly double.

And what makes a 3-D TV more expensive? (I haven't heard of anybody suggesting we'll see starting prices under $2,000.) Chalk that up to the extra processing power needed to keep the images in sync, the transmitter, faster screen-refresh technology and the glasses.