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LCD or Plasma Tv - which one is best ?
[b]Are there any differences between the two technologies?[/b]
When it comes to flat screen TVs the two technologies LCD and Plasma appear very similar with almost lifelike images and the ability to be hung on the wall. Although LCD tvs and Plasma tvs panels may look very similar in the stores, there are lots of differences between the two technologies.
How LCD tvs work
The LCD tv screen is a thin flat display device and is made up of a two clear panels which have many colour liquid crystal filled pixels that are arranged in arrays in between them. When a small voltage is applied to the crystals they twist or untwist repositioning themselves so that light can either pass through or it is blocked. When millions of crystals do this a picture is displayed. Very little power is used in this process. Behind the screen is a back light that illuminates the pixels and displays a colour depending on their colour (either red, blue or green), also areas of light and dark spots are displayed depending on how they are positioned. LCD devices are available in small sizes for items such as a watch up to 108 inches. Most television manufacturers produce LCD television including Hitachi, JVC, LG, Panasonic, Pioneer, Philips, Samsung, Sharp, Sony, and Toshiba.
How plasma tvs works
A plasma panel consists of millions of minuscule phosphor coated, gas filled cells or pixels with electrodes in them. Inert gases such as Xenon and neon fill the cells. When a current is applied to the electrodes in the cells it charges up the gas with positive and negative ions. As the ions become excited they collide with each other producing photons of ultraviolet light which react with the coloured phosphor coating in the pixels releasing red, blue or green light. When these colours are combined it is possible to create billions of colours. A panel consists of millions of pixels which together create the picture. The only manufacturers of Plasma televisions are LG, Panasonic, Philips, Pioneer, and Samsung who produce sizes of 32 inches up to 150 inches.
[b]How does the Picture quality and the performance compare?[/b]
Screen Brightness
LCD TVs can be brighter than plasma TVs. This perception of this brightness is of course reliant on where the TV is situated and what is being viewed. In reality both technologies are capable of producing a level of brightness that is in excess of what is required in normal viewing.
Contrast Ratio and Black Levels
The contrast ratio is a measure of the variance in light and dark tones that a panel can produce - in general a high ratio means greater details can be discerned. Historically LCD tv panels have had a poorer contrast ratio than plasma tvs because the backlight bleeds through darkened pixels and lightens the image. New advances in technology have created techniques to avoid light leakage, and increasecontrast ratios so that they are more comparable with Plasma tv, but still not as good. Because each cell on a plasma tv is able to be switched off rather than blocking the light as per LCD tvs the blacks are blacker. For a television picture, the black level is very important because black encompasses the entire spectrum of colour. And so, the deepest blacks create the richest colours and hence more realism. Devoid of deep black levels the colours look more 'pastel' like. Typically the black on an LCD tv screen is more 'grey' when compared to the plasma tvs black.
[b]Colour Saturation Levels[/b]
This is a measure of the correctness of the colours on the screen based on the existence of grey shades - the higher grey shades results in lower colour saturation. Plasma TVs have high colour saturation due to the way they emit light. The ability of Plasma tv pixels to be switched off when they are not in use stops the emission of stray light that diffuses colour. This is why tints and hues on Plasma TVs are noticeably more vivid and vibrant
Colour Gamut
The colour gamut is the set of possible coulors within a colour spectrum that a screen can display. The top end models of Plasma tv and LCD tv manufacturers are claiming that the colour gamut is near to the full spectrum. On comparable priced LCD tv and Plasma tvs, the Plasma tv again out performs the LCD tv on all but the top end models. The reason for this is that for the same manufacturers the colour gamut isnt as good on the lower models. On plasma tv models the cheaper models don't have such a difference compared to more expensive models from the same manufacturer.
Resolution
The screen resolution is a measure of the total pixels that makes the screen. The higher the definition, the higher the resolution and greater the detail and sharpness will be in the picture. LCD HDTVs have a resolution 1920 pixels x 1080 pixels or 1080P are, size for size, at a lower price than comparable Plasma tvs. 1080 is the vertical reolution and the P is for progressive scan because it isn't interlaced. The best Plasma tv and LCD tvs screens above 37 inches are HDTVs with the same 1080P resolution i.e. there is no difference. At sizes of 37 inches down to 32 inches the best LCD tv screens are still 1080P set but the Plasma tvs are lower resolution HD ready 720P (1280 pixels x720 pixels) models. There aren't any Plasma tvs smaller than 32 inches, but there are many LCD tv models.
Response Time and Refresh Rate
How a screen is able to deal with fast moving pictures without blurring is a combination of the refresh rate and the response times. The response time is a measure of the speed of a screen to quickly change when an input signal is received. Early LCD tvs had a lot of motion blur caused by slow response times because the pixels took too long to change from on to on to off, and back on to on to refresh the image. Improvements in screen technology has improved this response time to the point where it is no longer the cause of the motion blur. Now the cause is mainly the refresh rate or frame rate.
Lower model of LCD televisions and Plasma televisions operate at a frame rate of 50hz or 50 frames per second. In fact until recently, before 100hz models were launched, all models operated at 50 Hz. Now on more expensive models of LCD tv and Plasma tv motion blur is reduced with the addition of 100hz which create an extra frame that is placed between the normal frames. Because a normal signal is 50 Hz an additional middle frames is created by signal processing software that interpolates what the extra middle frame should look like. This results in picture motion that is more fluid and looses little if any definition. However the best Plasma tvs still show fast moving images better than the best LCD tvs but the difference is narrowing because the LCD tvs response time has reduced and 100hz and 200hz models have been established.
The Viewing Angle
This is the maximum side angle that a viewer can see the image on the screen clearly. Plasma tvs usually have a viewing angle of between 160 degrees to 180 degrees whereas LCD tvs have a viewing angle of around 100 degrees after which the picture dulls.
[b]The screen surface[/b]
LCD tv screens are available with matt finish screens which reduce glare while Plasma tvs have a reflective screen.
[b]Screen Burn-in[/b]
For Plasma tvs With prolonged displaying of non-moving images, graphics or text, such as a menu bar, channel logo, or news scroll a permanent ghost image can be permanently burned on the screen with a darkened appearance. SO even if the image on the screen is changed or removed it can't be removed for the rest of the plasma tvs life and is always seen as a shadow image. Regardless of how long a static image is displayed on an LCD tv they aren't affected by burn-in. But the problem of burn-in is exaggerated and unlikely under normal viewing.
[b]Screen Image retention[/b]
This is often confused with burn-in which appears to be similar but it isn't permanent. The 'ghost images' vanish quickly with image retention when a new bright image appears or after a few seconds. For technical reasons image retention is normal and present on Plasma tvs but hardly ever noticed. This effect can be minimised by having a 'break-in' period for the first 100 hours of the plasma tvs life. During this period you should watch programs that fill the whole screen and don't have any bright static images such as station logos or news scrolls at the bottom of the screen. You should also reduce the brightness and contrast to a middle level. The latest Plasma televisions have circuits built in to them to greatly reduce the chance of either image retention or burn-in.
[b]Is there any difference in power consumption of LCD tvs or Plasma tvs ?[/b]
The power consumption of an LCD tv is virtually constant because they have a back light that is on all of the time. The back light can be manually adjusted but uses less power on a low setting and more power on a high setting. The modulation of the LCD tvs screen pixels takes very little power.
Though Plasma tvs charge a gas to a plasma to produce light. The more light that is required the more often this is done. So it's normal for plasma tvs to want more energy on an image with high levels of brightness, and less energy on low brightness scenes. Accordingly the power consumption varies.
The energy requirements that are quoted for Plasma tvs are for full brightness settings. The effect of this is that lcd tvs seem to use less power than plasma tvs. But the power consumption of a plasma tv varies depending on the amount of dark and bright areas on the displayed image. Studies have found that when the viewed programs are mainly dark or on movies the amount of power consumed for plasma tvs will be lower than an lcd tv. However when the viewed programs are sports and cartoons the power consumption for plasma tvs is greater than on lcd tvs. When varied programs are viewed the power consumption is similar for LCD tvs and Plasma tvs. Future plasma tvs are going to consume less than half the amount power consumed at present.
[b]Plasma tv Life expectancy[/b]
Plasma tv manufacturers are nowadays quoting statistics of 100000 hours for the life expectancy. This represents a usage level of almost 11.5 years of non stop use. As a result any concerns regarding the life expectancy of plasma tvs being less than LCD tvs are unfounded.
Conclusion
Both technologies have benefits. Plasmas tvs usually have a superior subjective picture with better black level, higher contrast, and superior colour rendering than LCD TVs. Though LCD TVs have higher brightness, and no screen burn-in worries, and are lighter and thinner. This is not always the case sincea good LCD TV may have a better picture than an average or poor plasma TV. But on balance I believe that a plasma tv is the superior option with more advantages. At the end of the day you get what you pay for so spend as much as you can manage to pay for on you preferred format.
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