Since I find myself under constant questioning lately by everyone whose half sister on some remote planet in a galaxy far far away and is thinking about maybe buying a new TV, I thought I'd share with you some of the highlights of "Moshe's abridged guide to moving imagery at home".
Hope you'll find it interesting.
Before we start I'll just remind you of the task at hand when choosing your new TV: You want the picture to look as real as possible and the size to be as impressive as possible (which usually means as big as possible, although with today's projectors you can easily go over the top).
This point is important to emphasize, since most people seem to just want the brightest picture out there, and bright does not necessarily mean good. In fact, in most cases it means the other way around.
The sad reality is that TV manufacturers set their sets to be on the brighter side of things because they know it's the brighter set that would attract the eye of the viewer at the shop floor, just like it would be the louder speakers that would attract the ears of the listener. That is why speaker testing/comparison should be done at equal sound levels, and that is why monitor comparison should be done on calibrated sets (calibrated to follow the proper standards - yes, there is such a thing).
Alas, such calibration is something one can never get. By now I know that I can listen my way through the good audio and the bad one, but I cannot say the same about video (if only because I haven't done it much). Which means that most of what I know about monitors comes from reading, which in actual fact is not that different a situation to the audio scene.
Another similarity between audio and video is the total lack of reliability of the manufacturers published specifications for their monitors. Anything that cannot be easily measured (e.g., resolution) is usually just a figment of the imagination (or something the manufacturer went out of its way to come up with). For example, most monitors will specify a contrast ratio of 1:2000 or something similar; reality will show that it's more like 1:100 - 1:200, and the simple reason for that is that the manufacturer measures the difference between an all black picture and an all white picture while for us what really matters is the difference between the white and the black in the same picture. And then there's the issue of "what's contrast in the first place", and believe it or not, there is a lot of inconsistency here, too.
Intros aside, let's have a brief look at the projection technologies one can put a hand on at the moment:
1. CRT: The old cathode ray is still the one to beat when it comes to picture quality. However, given it needs a vacuum tube to run, it is impractical to have sets bigger than 36". CRT projectors also provide awesome quality, but their light output deteriorates quickly and you simply must watch them in an absolutely dark room. Both factors - size and lack of brightness - mean that CRT technology is doomed to serve as high quality, small size TVs for the spare room.
2. LCD: I'm sure you know how this one works - a light source from behind the monitor passes through a green layer, a red layer, and a blue layer, all of which determine the final color you see. Its biggest disadvantage is that blacks are not real blacks - they are not "zero light", but rather light that passes through all three filters. As a result you get washed out blacks and low contrast levels.
3. Plasma: Plasmas are made of small pixels of gas which generate light when excited by electricity. One excited pixel becomes red, the other green, etc. Due to the gas getting tired with time you get side effects such picture burn if you play the same frame for a long time and a general deterioration after a long while; however, those are really very long term effects.
4. DLP: A personal favorite. A lamp lights a rotating prism which passes only blue light one fraction of a second, then green light, and then red light on to a chip that contains lots and lots of quickly revolving mirrors; if the mirror is open, the light passes, and if it's closed, it's a black dot. Over a few such revolutions you get a nice picture thrown on the wall.
5. LCOS: Short for Liquid Crystal on Silicone, this is a similar concept to LCD only that it happens on a chip. Because the chip is enclosed, blacks are way better; and because of that, this technology is considered the most promising - potentially, better than CRT.
Now the question that most people ask is: Should I get plasma? LCD?
The answer is that it doesn't matter which technology you get as long as the picture is good. That said, each technology has its characteristics; I'm not talking about "brightness" and "contrast", I'm talking things like gamma behavior (how colors change with the change of the input signal) and gray scale tracking (how the b/w content of the picture is managed). There's more to it, but the point is that there are things we layman were never told at the department store where no one knows anything about TVs in the first place.
Personally, I don't like plasmas' character - doesn't seem real. That said, there are good ones out there. I don't like LCDs much because of their washed blacks, but that said, there are good ones out there. I've never seen LCOS yet, which leaves DLP as my prime time favorite for a bug picture; but here, too, one can easily fall with the more inferior specimen.
Next time: direct view vs. projection, interlacing vs. progressive, and high definition resolutions.