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Why is picture quality much better on CRT based TVs than LCD or Plasma?


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#1 of 5 OFFLINE   Tracy_Smith

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Posted March 31 2003 - 02:14 PM

Why is the picture quality so much better on CRT based TVs (those with picture tubes) than LCD or Plasma screens? What has to change in LCD or Plasma screensto make their picture quality closer to CRT output quality? How does HDTV figure in the equation? Seems like HDTV CRT based TVs still look better than HDTV flat screens? Thanks Tracy

#2 of 5 OFFLINE   Jeff Kleist

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Posted March 31 2003 - 04:55 PM

It's not "better", it's just brighter.

#3 of 5 OFFLINE   Cees Alons

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Posted April 01 2003 - 02:46 AM

The gap is closing quickly.

TV (as a technology) was created around the analogue CRT tube. It wasn't digital, the image was "written" (and transmitted) along horizontal lines, one after another and the lines themselves weren't even in the proper order.

Much development went into CRT and they became as good as they are now. But to get even bigger images, CRT can no longer be used in common household environments (simply said: too heavy), so we needed something else. LCD and plasma screens were developed (in the PC industry first) and they are digital. Not just the signal, but the structure of the screen too (pixels). And in the early stages of development, the colour-depth and contrast weren't as good as in CRTs yet. The first LCD screens were "slow" (after-images), so moving images (=movies Posted Image ) weren't that good either.

Furthermore, the much larger screens make it even more difficult to display a (limited resolution) image on a pixel based screen and still make it look beautiful. They have to add special circuitry and edge enhancement and other tricks. To judge it, you need to have to screens of exactly equal size - and preferrably HDTV (to make up for the conversion problems when going from low-res analogue to medium-to-high-res digital).

But generally speaking, I'd say that your statement already is no longer true: at least not the "much" part of your question!

Cees

#4 of 5 OFFLINE   Jack Briggs

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Posted April 01 2003 - 04:27 AM

Well, to a certain extent. CRTs still rule when it comes to rich, deep black levels, and that lends their pictures such dimensionality and depth. A plasma panel will have just as much light output as a CRT-based design, but it still has a way to go before achieving that lifelike black level.

LCDs are even more afflicted by this situation.

#5 of 5 OFFLINE   Leo Kerr

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Posted April 02 2003 - 04:13 AM

A couple things, really.

One is the compromises that they make. With LCD screens - and projectors for that matter - there are a number of inter-related variables: brightness, contrast, color saturation and purity, viewing angle, and screen-door effect are just some of them. For example, you can get wonderful contrast, color, and brightness, but your viewing angle and screen door goes to snot. If you want viewing angle and lack of the screen-door, then your color purity, saturation, and contrast are shot.

With plasma screens, I'm not sure. My understanding of the technology says that they should be wonderful. My experience is that they are rotten. At least until you hit the $25,000 price range, and then they're sort of iffy at best. (There seem to be tremendous variation between serial numbers in the same lot.)

CRTs also do some wonderful analog filtering - smoothing, if you will - that really do a good job of fooling your eyes into seeing things that aren't there - or not seeing things that are there.

Leo Kerr
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