Plasma and LCD technology — what's the difference?

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Offline R i Y a D

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Plasma and LCD technology — what's the difference?
« on: May 10, 2010, 10:43:36 PM »
Plasma and LCD panels may look similar, but the flat screen and thin profile is where the similarities end. Plasma screens, as its name suggests, uses a matrix of tiny gas plasma cells charged by precise electrical voltages to create a picture. LCD screens (liquid crystal display) are in layman's terms sandwiches made up of liquid crystal pushed in the space between two glass plates. Images are created by varying the amount of electrical charge applied to the crystals. Each technology has its strengths and weaknesses, as you'll read below.

Advantages of plasma have over LCD?

Apart from better contrast due to its ability to show deeper blacks, plasma screens typically have better viewing angles than LCD. Viewing angles are how far you can sit on either side of a screen before the picture's quality is affected. You tend to see some brightness and colour shift when you're on too far of an angle with LCDs, while a plasma's picture remains fairly solid. This is steadily changing, with more and more LCDs entering the market with viewing angles equal to some plasmas. Plasmas can also produce a brighter colour, once again due to light leakage on an LCD affecting its colour saturation.

Plasma pundits will also tell you that some LCD screens have a tendency to blur images, particularly during fast-moving scenes in movies or in sports. While that was true for older generation LCD screens, newer models have improved significantly — so much so that the differences in performance between LCDs and plasmas in this regard is almost negligible. (While the pixel response time, measured in milliseconds (ms), can give you some indication of an LCD's performance with fast-moving scenes, it's not always reliable.)

Advantages of LCD over plasma

Apart from becoming increasingly price competitive, LCD has the edge over plasma in several other key areas. LCDs tend to have higher native resolution than plasmas of similar size, which means more pixels on a screen.

LCDs also tend to consume less power than plasma screens, with some of the newer "Eco" LCD panels able to use half of the power than equivalent plasmas, with the trade-off being lower brightness.

In terms of bulk, LCDs are also generally lighter than similar-sized plasmas, making it easier to move around or wall mount. This is because LCDs use plastic in their screen make-up whereas plasmas tend to use glass.

LCD pundits point to the belief that LCDs have a longer lifespan than plasma screens. This may have been true of earlier plasma models, which would lose half of their brightness after more than 20,000 hours of viewing. However, many plasmas available on the market today quote a lifespan of about 60,000 hours, which is the same as LCD. This means they will last for almost seven years if left on 24 hours a day.

You might have also heard that plasmas suffer from screen burn-in, an affliction not commonly associated with LCDs. Screen burn in occurs when an image is left too long on a screen, resulting in a ghost of that image "burned in". Newer plasmas are less susceptible to this thanks to improved technology and features such as screensavers, but burn-in can still be a problem. However, after a few days most burnt-in images will fade — they are no longer permanent.
Mahmudur Rahman
RF Optimization Engineer
Radio Network Planning & Optimizations
ZTE Corporation Bangladesh Limited