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LCD Monitors and Contrast Ratio

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Written by Andrew Lomar   
Saturday, 14 March 2009 18:33

The technical aspect that anybody wanting to buy a LCD television is concerned about is most probably the contrast ratio, since it's clear that the higher it is, the better the performance.
To be precise, there are two kinds of so called “contrast ratio”. The first is the static contrast which is the ratio between the brightness of the white and the brightness of the black. It is a value that shows how much the liquid crystals in the panel are capable to block the light coming from the backlight lamp.
The second kind is the dynamic contrast, which doesn't only depend on the liquid crystals, but on the backlight too. As a matter of fact it is the ratio between the white calculated on the maximum backlight and the black calculated on the minimum backlight. This dynamic ratio is thus much higher than the panel static one.

Brightness and backlight

Brightness is a very important feature when deciding for a LCD. Liquid crystals television monitors have a very high brightness, due to hundreds of foot candles per square meter. It is this characteristic that makes LCD displays perform extremely clear images even in a room with strong ambient light, but it can create problems when the ambient is too dark.
The strong backlight increasing the panel's brightness is directly connected to the dynamic contrast ratio, so that enhancing the brightness means raising the dynamic contrast.

What is Local Dimming?

The basic principle of the Smart Lighting, a.k.a. Local Dimming technology, is quite easy: instead of having various lamps constantly switched on behind the liquid crystal panel, a LEDs matrix is placed in the back of the television.These LEDs can switch on and off separately according to the brightness in different sections of the image.
This way the dynamic contrast ratio is increased not by enhancing the backlight but lowering the black level to the minimum due to the LEDs switching off.
Local dimming is as much effective as much as there is a direct action on the screen pixels.
The ideal situation would be to place a LED behind each RGB component (that's more than 2 millions in full HD displays) of the pixels in the panel.
At the moment that's totally impossible both for the very high producing costs and because it needs a very complex managing software.
So the screen is simply divided into sections, each one controlled by a single LED switching on and off.
At the moment the televisions with Local Dimming on the market are divided into about 100 different sections, but this number is quickly increasing and that improves more and more the performance of these devices.

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Comments
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john p   |93.42.84.xxx |2009-05-22 04:05:28
What is the contrast ratio on lcd monitors? is a higher contrast ie 450-1 better
or worse than 250-1 Thanks
rac  - re:   |93.42.84.xxx |2009-05-22 04:06:43
john p wrote:
What is the contrast ratio on lcd monitors? is a higher contrast ie 450-1
better or worse than 250-1 Thanks

The contrast ratio is the brightness of the pixil over the brightness of
the background. Higher is better (500:1 better than 300:1)
Zip TV Installation Pro   |75.146.46.xxx |2009-06-11 23:07:54
Very informative information that all should know.
Thanks!
moustafa  - News&Reviews about Computers and Laptops   |41.237.205.xxx |2010-02-17 12:51:54
The most important factor in LCD televisions is the contrast ratio which makes
images appear more clearer.

Visit my site to find much
reviews.

www.choosecomputer.net
ArticleDirectoryLand  - Free Articles   |122.161.228.xxx |2010-02-17 18:06:54
Thanks for this nice info sharing. You can also find more free articles about
LCD TVs on this article directory.
Ardi   |91.187.103.xxx |2010-04-21 10:45:22
Quote:
Liquid crystals television monitors have a very high brightness, due to
hundreds of foot candles per square meter.


I kept telling that to a friend when he wanted to buy a TV but he
wouldn't trust me, now I've got proof!
TwilightFan  - re:   |91.187.103.xxx |2010-05-17 16:43:54
Ardi wrote:
Quote:
Liquid crystals television monitors have a very high brightness, due to
hundreds of foot candles per square meter.


I kept telling that to a friend when he wanted to buy a TV but he
wouldn't trust me, now I've got proof!


Yes, that's right, tell him that. Never pick a liquid crystal TV,
ever,

TwilightFan
samuel  - re: News&Reviews about Computers and Laptops   |91.187.103.xxx |2010-05-17 17:20:57
moustafa wrote:
The most important factor in LCD televisions is the contrast ratio which
makes images appear more clearer.


do plasma tvs have this ratio?
erwin   |91.187.103.xxx |2010-05-18 11:42:48
i dont think so, i thiNk this makes LCD better and special
charline   |91.187.103.xxx |2010-05-18 11:03:20
thats exactly what i dont like about crystal liquid monitors, they have a higher
brightness than it should really be
Gwen   |91.187.103.xxx |2010-05-18 11:13:24
Cant you just adjust the brightness yourself?
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