What is the difference between the flat screen technologies ?
Both LCD tvs and Plasma tvs appear to give similar levels of performance. So is there any real difference? Both are slim and can be hung on the wall. Many people will incorrectly refer to small screens as plasma tvs when they are LCD tvs. However both technologies work and perform very differently. What is the difference between the two technologies?
How does an LCD (Liquid Crystal Display) television 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 tv screen comprises of millions of minute 'light bulbs' which are small glass cells filled with inert gases such as xenon and neon. These cells are illuminated by a current being applied to electrodes in the gas filled cell and its atoms become 'excited' to a plasma and emit photons of ultraviolet light. These photons in turn hit a phosphor coating which emits visible light. The colour of the visible light emitted by each cell depends on the three different coloured phosphors - red, blue and green, and can together produce billions of colours when combined. As with the LCD tv screen, the millions of cells intermix to form the image on the screen. Currently the only manufacturers of Plasma tvs in the UK are Samsung, Philips, LG, Panasonic, and Pioneer. Plasma tvs are existing in sizes from 32 inches to 150 inches.
How does the Picture quality and the performance compare?
The Brightness of the picture
The picture on LCD tv screens can be brighter than Plasma tvs. Depending on where the television is located and what is being viewed will determine how this difference in screen brightness is perceived. However both Plasma tv and LCD tv screens are capable of producing brightness levels that in normal viewing conditions are in excess of what is needed.
The effect of the Contrast Ratio and the Black Levels.
The contrast ratio is a measure of the difference in light and dark tones that a panel can produce - in the main a high ratio means greater details can be discerned. Historically LCD tv panels have had a lower contrast ratio than plasma tvs because the backlight bleeds through darkened pixels and lightens the image. New advances in technology have created techniques to thwart 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 generate the richest colours and thus 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.
Levels of Colour Saturation
The colour saturation measures the accuracy of how colours are presented on the screen in the presence of grey shades. A higher grey shade will result in lower colour saturation. The colour saturation of a Plasma tv screen is high because of their black levels, their low grey shades, and their ability to switch off pixels when they aren't in use, thus preventing colours being diffused by the stray light emissions. Hence the tints and hues are visibly more colourful and more life like.
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.
TV Screen 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'20 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.
Refresh Rate and Response Time of the screen
These two attributes in combination influence how fast a moving picture a screen can reproduces without the image blurring. Response time is a gauge of how fast a screen can vary when an input is received. Historically LCD tv panels had slow response times which was the limiting factor causing motion blur because each pixel has to go from an on state, to an off state, and back to on in order to refresh an image. Improvements in pixel response times on LCD tv screens means that the actual response time isn't the main cause of motion blur, its generally caused by the refresh rate, or the 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 a measure of how far off axis you can view the picture before it fades. The viewing angle of a Plasma television is between 160 degrees to'0 degrees. On an LCD television the viewing angle is about 100 degrees at which point 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.
Image Burn-in
This can result if a static image is displayed on the screen for a prolonged time, and even after the image is changed or removed, the 'ghost image' of the previously displayed static image is still detectable on the screen for the remainder of the screens life. burn-in doesn't happen on LCD tvs. Though the probability of burn-in on plasma tv is usually exaggerated and unlikely.
Image retention
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.
How does the Power consumption of LCD tv and Plasma tv compare ?
LCD tvs have a backlight that is constantlyon and uses virtually constant power. LCD tvs usually have an adjustable back light which uses extra power when it is on a high setting and less on a low setting. The power required to alter the pixels is infinitesimal.
On a plasma tv the gas is charged in each of the pixels to emit light. When more light is in a scene the plasma tv uses more energy. When the brightness is high the plasma tv use more energy and when the brightness is low the plasma tv uses less energy. So the power consumption will vary depending on what is being displayed.
On paper it may seem that the Plasma tvs consume a lot more power than LCD tvs. Plasma tv manufacturers tend to quote the most power usage at full brightness. However the plasma tvs power power consumption changes depending on the signal and the amount dark and bright areas on the screen. Studies have shown that when viewing mainly dark programs and movies the average power power consumption of an equal sized plasma tv is in reality lower than LCD tv. However if lots of cartoons and sport are viewed then the LCD tv uses less power. Accordingly on average with varied viewing content there is little difference between LCD tvs and Plasma tvs. Plasma tv manufacturers are shortly going to be launching models that will reduce the power consumption by over half.
[b]Plasma tv Life expectancy[/b]
Plasma tv manufacturers are nowquoting figures of 100000 hours for the life expectancy. This represents a usage level of just about 11.5 years of non stop use. Thus any concerns about the life expectancy of plasma tvs being less than LCD tvs are unfounded.
[b]Conclusion - which should you buy?[/b]
Both technologies have advantages. Plasmas tvs typically have a better subjective picture with healthier black level, higher contrast, and superior colour rendering than LCD TVs. Although LCD TVs have higher brightness, freedom from screen burn-in worries, and are lighter and thinner. This is not always the case becausea good LCD TV may have a better picture than an average or poor plasma TV. Nevertheless on balance I consider that a plasma tv is the superior option with added advantages. In the end you get what you pay for so spend as much as you can manage to pay for on you preferred format. - 29954
Both LCD tvs and Plasma tvs appear to give similar levels of performance. So is there any real difference? Both are slim and can be hung on the wall. Many people will incorrectly refer to small screens as plasma tvs when they are LCD tvs. However both technologies work and perform very differently. What is the difference between the two technologies?
How does an LCD (Liquid Crystal Display) television 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 tv screen comprises of millions of minute 'light bulbs' which are small glass cells filled with inert gases such as xenon and neon. These cells are illuminated by a current being applied to electrodes in the gas filled cell and its atoms become 'excited' to a plasma and emit photons of ultraviolet light. These photons in turn hit a phosphor coating which emits visible light. The colour of the visible light emitted by each cell depends on the three different coloured phosphors - red, blue and green, and can together produce billions of colours when combined. As with the LCD tv screen, the millions of cells intermix to form the image on the screen. Currently the only manufacturers of Plasma tvs in the UK are Samsung, Philips, LG, Panasonic, and Pioneer. Plasma tvs are existing in sizes from 32 inches to 150 inches.
How does the Picture quality and the performance compare?
The Brightness of the picture
The picture on LCD tv screens can be brighter than Plasma tvs. Depending on where the television is located and what is being viewed will determine how this difference in screen brightness is perceived. However both Plasma tv and LCD tv screens are capable of producing brightness levels that in normal viewing conditions are in excess of what is needed.
The effect of the Contrast Ratio and the Black Levels.
The contrast ratio is a measure of the difference in light and dark tones that a panel can produce - in the main a high ratio means greater details can be discerned. Historically LCD tv panels have had a lower contrast ratio than plasma tvs because the backlight bleeds through darkened pixels and lightens the image. New advances in technology have created techniques to thwart 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 generate the richest colours and thus 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.
Levels of Colour Saturation
The colour saturation measures the accuracy of how colours are presented on the screen in the presence of grey shades. A higher grey shade will result in lower colour saturation. The colour saturation of a Plasma tv screen is high because of their black levels, their low grey shades, and their ability to switch off pixels when they aren't in use, thus preventing colours being diffused by the stray light emissions. Hence the tints and hues are visibly more colourful and more life like.
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.
TV Screen 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'20 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.
Refresh Rate and Response Time of the screen
These two attributes in combination influence how fast a moving picture a screen can reproduces without the image blurring. Response time is a gauge of how fast a screen can vary when an input is received. Historically LCD tv panels had slow response times which was the limiting factor causing motion blur because each pixel has to go from an on state, to an off state, and back to on in order to refresh an image. Improvements in pixel response times on LCD tv screens means that the actual response time isn't the main cause of motion blur, its generally caused by the refresh rate, or the 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 a measure of how far off axis you can view the picture before it fades. The viewing angle of a Plasma television is between 160 degrees to'0 degrees. On an LCD television the viewing angle is about 100 degrees at which point 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.
Image Burn-in
This can result if a static image is displayed on the screen for a prolonged time, and even after the image is changed or removed, the 'ghost image' of the previously displayed static image is still detectable on the screen for the remainder of the screens life. burn-in doesn't happen on LCD tvs. Though the probability of burn-in on plasma tv is usually exaggerated and unlikely.
Image retention
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.
How does the Power consumption of LCD tv and Plasma tv compare ?
LCD tvs have a backlight that is constantlyon and uses virtually constant power. LCD tvs usually have an adjustable back light which uses extra power when it is on a high setting and less on a low setting. The power required to alter the pixels is infinitesimal.
On a plasma tv the gas is charged in each of the pixels to emit light. When more light is in a scene the plasma tv uses more energy. When the brightness is high the plasma tv use more energy and when the brightness is low the plasma tv uses less energy. So the power consumption will vary depending on what is being displayed.
On paper it may seem that the Plasma tvs consume a lot more power than LCD tvs. Plasma tv manufacturers tend to quote the most power usage at full brightness. However the plasma tvs power power consumption changes depending on the signal and the amount dark and bright areas on the screen. Studies have shown that when viewing mainly dark programs and movies the average power power consumption of an equal sized plasma tv is in reality lower than LCD tv. However if lots of cartoons and sport are viewed then the LCD tv uses less power. Accordingly on average with varied viewing content there is little difference between LCD tvs and Plasma tvs. Plasma tv manufacturers are shortly going to be launching models that will reduce the power consumption by over half.
[b]Plasma tv Life expectancy[/b]
Plasma tv manufacturers are nowquoting figures of 100000 hours for the life expectancy. This represents a usage level of just about 11.5 years of non stop use. Thus any concerns about the life expectancy of plasma tvs being less than LCD tvs are unfounded.
[b]Conclusion - which should you buy?[/b]
Both technologies have advantages. Plasmas tvs typically have a better subjective picture with healthier black level, higher contrast, and superior colour rendering than LCD TVs. Although LCD TVs have higher brightness, freedom from screen burn-in worries, and are lighter and thinner. This is not always the case becausea good LCD TV may have a better picture than an average or poor plasma TV. Nevertheless on balance I consider that a plasma tv is the superior option with added advantages. In the end you get what you pay for so spend as much as you can manage to pay for on you preferred format. - 29954
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