What is the difference between the flat screen technologies ?
Most people are not aware of the difference between LCD televisions and Plasma televisions. Quite often people will refer to a flat panel tv as a Plasma tv or an LCD tv incorrectly as a generic term. e.g. a 26 inch Plasma tv, a size of Plasma tv that doesn’t exist. What they actually mean is a 26″ LCD screen. So what are the differences between them and how do you spot them? Both flat panel technologies can be hung on the wall and can produce unbelievably realistic images that make you feel that you are there.
LCD screens explained
LCD means Liquid Crystal Display. The LCD tv screen is a thin, flat display device comprised of two clear panels that have a number of colour liquid crystal-filled pixels arrayed between them. The crystals twist or untwist and reposition themselves to either let light pass through or block light and this results in a picture being displayed when millions of crystals do this together. The reposition of the crystals is triggered by a small voltage and uses very little power. The LCD tv screen is backlit so this behaviour creates light or dark spots on the screen and colour depending on the pixels that are repositioned. LCD tvs are available in sizes from a few inches to over 108 inches. All leading manufacturers have LCD televisions including Sony, Panasonic, Philips, JVC, Toshiba, Hitachi, Samsung, LG, Pioneer and Sharp.
How does a Plasma screen display a picture?
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.
Performance and Picture quality compared
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 difference between the extreme of light and dark tones is known as the contrast ratio. Usually the greater the contrast ratio is the more details can be differentiated. In the past LCD tv screens were known to have lower contrast ratios than plasma tvs due to the pixels not being able to totally block the back light on darkened pixels and light would bleed through and make the image lighter. New methods of reducing this light leakage have been introduced on the latest LCD tv screens so that the contrast ratios are closer to those of a Plasma tv. However Plasma tvs are still better because their pixel cells can be switched off, rather than blocking the back light with LCD tvs, and blacks are blacker. The black levels on a television underpins the overall picture quality. If the blacks aren’t black enough then the whole colour palette or colour saturation is affected so that the colours appear artificial rather than life like. The black level on an LCD tv is more dark grey when compared with the black level on a plasma tv.
Levels of Colour Saturation
This is a measure of the correctness of the colours on the screen based on the presence 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 prevents the emission of stray light that diffuses colour. This is why tints and hues on Plasma TVs are noticeably more vivid and vibrant
The Colour Gamut
Is the range and number of colours that can be displayed. The most expensive models are now claiming to have colour gamut’s getting fairly close to the full spectrum for plasma tv and LCD tv. In fact most plasma TVs tend to be better than most LCD tvs except the top of the range ones. With the cheapest LCD tv models more often than not offering a colour gamut that isn’t as good the higher LCD tv models. So as a rule the plasma tv has the best colour gamut.
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
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.
Less expensive models of Plasma televisions and LCD televisions operate at frame rates of 50 frames per second or 50hz. Recently 100hz tv models were launched on more expensive models which reduced motion blur by creating an extra middle frame which is placed in between the normal frames. This middle frame is created by advanced signal processing software that interpolates what the middle frame would look like. The addition of the middle frame results in moving images that are fluid with little, if any definition loss. Even with 100hz the best plasma tvs still out perform the best LCD tv models but by a narrowing margin because of reduced response times and 100hz and 200hz.
The Viewing Angle of the screen
Pictures on plasma TVs are nevertheless clearly viewable at about 160 degrees and on some models up to’0 degrees. However the picture dulls beyond about 100 degrees.
[b]The screen surface[/b]
A plasma tvs screen is a shinny reflective surface which can suffer from glare depending on the room conditions, whereas LCD tv screens have matt finish that reduces glare.
Image Burn-in
This is characterised by a ‘ghost image’ of a previously displayed static image that had been displayed for a prolonged period of time and is still present. Even if the screens image is changed from the original ‘ghost image’ or removed it is present for the rest of the plasma tvs life. For LCD tv screens burn-in isn’t a problem no matter how long the static image is displayed. Nonetheless the burn-in risk is overstated and improbable in normal viewing conditions.
[b]Screen Image retention[/b]
image retention is often confused with burn-in which has similar characteristics. However image retention is a ‘ghost image’ that appears on a plasma tvs after a still picture has been displayed for an extended period of time, but then disappears when a bright new image is displayed. Or it vanishes after a few seconds. By having a ‘break in’ period of about 100 hours from new, this can be minimised. Whist watching programs during this break in period care should be taken to watch programs that don’t have any static bright images like station logos and scrolling news headlines at the bottom of the screen. Also try to watch programs that fill the whole of the screen. It recommended that during this period the brightness and the contrast is kept at about a mid level. These characteristics of image retention and burn-in have been greatly reduced by technical improvements to reduce the possibility of burn-in or image retention.
How does the Power consumption of LCD tv and Plasma tv compare ?
The backlight on an LCD tv is constantly on so the power consumption is almost constant. By manually adjusting the brightness of the back light up or down the power consumption is either increased or decreased. The twisting and untwisting of the LCD pixels consumes hardly any power.
But 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 usual for plasma tvs to need 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.
Life expectancy of Plasma televisions
Plasma tv manufacturers are nowadays quoting figures of 100000 hours for the life expectancy. This represents a running level of just about 11.5 years of continuous use. Accordingly any concerns regarding the life expectancy of plasma tvs being less than LCD tvs are unfounded.
[b]Conclusion - which should you buy?[/b]
Both technologies have benefits. Plasmas tvs usually have a better subjective picture with healthier black level, higher contrast, and better 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. Although on balance I believe 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.
For the finest advice and the lowest prices with the finest service go to Cheap LCD tv’s and Plasma tv’s. To save even more money check out the Clearance sale of LCD tv’s and Plasma tv’s.
