You cannot fail to have noticed the way 3D viewing has become all the rage these days, both in the cinema (where it started) and in the home with 3D televisions. Without going into the long history of 3D development which has brought it to its current state, there are a few points which are worth making.
There are two kinds of 3D video technology which can be summarised as "passive" and "active". In the cinema it is the passive form. This means the inevitable spectacles are simple pieces of polaroid material, quite cheap, and the digital projection is of two images which are filtered by the glasses so one image is seen by the left eye and the other by the right eye: much better than the fifties 3D versions (remember Vincent Price in "The House of Wax"?) where the glasses contained acetate film of two different colours which interfered with the colour rendition of the image and which gave different light intensities to each eye.
3D television uses the active form, except for the LG company which is championing the passive form. Active 3D imaging uses expensive spectacles which have electronics built into them and which are synchronised with the image on the screen. It's called "active shutter technology". The image on the tv screen very quickly alternates between two versions, one for the left eye and one for the right eye. When it's displaying the image for the right eye, the left glass of the spectacles goes dark and prevents light reaching the left eye: vice versa with the following image, and so on.
Now this rapid switching of light to each eye is not everyone's cup of tea. Indeed, there have been reports of induced nausea and headaches by viewers. If you decide to embrace 3D technology, do test yourself in the shop before you buy to see if you react in that way. Give yourself plenty of time to watch the demonstration screen. It's clearly a personal response: some people will be affected and others not.
There are also technical problems associated with this rapid switching on the screen. All LCD tvs have a response time, which has been reducing as the technology advances. This is the time it takes for the tv screen to "lose" one frame while generating the next frame, essentially. The longer the response time of the screen, the slower will the screen be to change frames, resulting in some very peculiar artefacts on the screen. Bearing in mind that, in general, you're watching twenty-five frames each second (there are variations on this, depending upon the tv set and what you're watching), so we're talking about very small intervals of time. Nevertheless, LCD screens tend to have a slower response time than plasma screens, all other things being equal.
To display active 3D images, the switching involved should not leave any traces of a preceding frame, otherwise the integrity of the 3D image can be compromised. If you decide to go for 3D, do compare a plasma tv set with an LCD tv set, side by side (though you'll have to switch spectacles between looking at each one).
Regular 3D tv broadcasting is some way off yet. The major current source of 3D material is from the high-definition Bluray discs, where they contain a 3D version of the film. You would need a 3D-enabled Bluray player and a 3D-enabled television or projector to watch such discs. Most manufacturers currently include a few 2D-only sets in their catalogue, though they will be at the cheaper end of the range. Most R&D is going into 3D sets so they will have the latest technology even for producing a good 2D picture. It may be, therefore, that you would end up buying a 3D set but use it only to view 2D pictures. You can't help feeling you would be paying for something you're not going to use, but there's little alternative. It's like the gentleman who, visiting a tailors, finds just the suit for him but it's a three-piece and he doesn't want the waistcoat. Upon being asked about that, the salesman replies that the waistcoat is optional; it doesn't have to be worn!
Next time we'll be looking at the question: when is an LED tv actually an LCD tv?
