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Hot on the heels of the movie Avatar, this year's CES was touting 3D as the "next big thing" in home theatre. Manufacturers, hoping to prolong the boost in sales they got following the conversion to digital flat-panel HDTVs, are hoping to convince consumers, in a few years, to go through buying a whole new TV in order to view things in 3D.

Obviously, it's going to be a hard sell: while football in 3D might be tempting, needing to buy a dozen pairs of glasses in order to have a super bowl party hardly seems around the corner, notwithstanding the fact that not many people want to be seen wearing 3D glasses when there are other people around. At least at the movie theatre everyone is in the dark!

Rather than tread the ground most commonly covered, though, I want to weigh in on the whole discussion with two things I recently saw, one from the distant past and one from the "future".

I'll start with the future, since I'm disregarding the conventions of chronology anyway! This is the technology that allows TVs to be in 3D without wearing glasses. This exists, I've seen it at tech conferences, and it works, although it can make you queasy. It also adresses the problem of wearing goofy glasses that I mentioned above. Is it the future, though? Maybe someday, but for now the costs put it much farther into the future than the technologies currently being touted by television manufacturers. And while it does work, it is nowhere near as impressive as 3D in a movie theatre, for the simple reason that the screen is smaller. The 3D image can only go as far as the screen frame, you see, so it is not possible to have things flying all around you the same way they do at the theatre: depth has to be reduced just like the height and width of the picture, with the result that the 3D effect is that much less impressive. (In other words, this picture is totally fake—it is impossible for the shark's fin to cover up the frame of the TV!) You don't have things flying all around the room; it's more like your TV becomes the frame of a diorama. This is just as true with the systems that use glasses as with those that don't.

The other thing I saw recently was a museum of World War I memorabilia. In addition to guns, uniforms, and gas masks, it also had a large collection of stereoscopes, which displayed slideshows in 3D of a number of fascinating pictures taken during the war. Seeing this made me realise two things. Firstly, that 3D is nothing new. The stereoscope has been around since 1840. But it hardly managed to dislodge the photograph to become the "next big thing". Second, while 3D images are fun to look at, they don't really look like reality does. In fact, the 3D we get from perspective in an ordinary photograph is just as true to what we see when we look around in the real world as a 3D image is. This may seem counterintuitive, but it is true: the reason is that in a 3D stereoscope or movie, you can't actually see around things: the 3D you see is what was filmed by the cameras. So when you tilt your head, things move in 3D, but in an odd way that is not like what happens when you move your head in a real room. In real life if I tilt my head while looking at a tree trunk, I can see behind what I was looking at before. In a 3D movie, the whole scene shifts so that I still see the same things as before. I can't see behind anything, because both the foreground and background re-arrange themselves to present the same picture again. It's a neat effect, but it's nothing like reality.

True "3D" in imitation of reality requires a hologram, which actually does record an image from multiple angles. I have seen, in a museum, holograms in which enough angles are recorded that you can walk all around them, and they are quite a feat, despite not being in full colour. But even a 5 second "animation" in a hologram takes a huge amount of time to create. Holographic movies are decades away, I have to think. Besides which, the "animation" is played by walking around the hologram. I am not aware of any way to play a holographic "movie" in the way we are used to thinking of movies today. Advancements are needed not only in technology but in science before we can seriously consider this as a future possibility.

So anyway, I thought those points were worth sharing on the topic. I do enjoy 3D movies and will continue to see them, but it is important to realise that they are nothing new, not as impressive on a small screen, and not actually more realistic than 2D movies. All of which leads me to believe that we will not be replacing our existing HDTVs any time soon.