Plasma TV Reviews

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.

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 does a Plasma television work ?

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.

A comparison of the Picture quality and Performance

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.

Black Levels and the Contrast Ratio

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.

Colour Saturation Levels

colour saturation is a measure, in the presence of grey shades, of colour purity or how accurate the colours are on the screen. The higher the colour saturation the more accurate the colour rendition. With blacks that aren’t as black the grey shades will be higher resulting in a lower colour saturation. Plasma offer better levels of colour saturation due to better black levels because of their ability to switch of pixels that aren’t in use, preventing diffusion of colours by stray light emissions. This results in hues and tints that are more life like colourful.

The Colour Gamut

The colour gamut is a measure of the number of colours that a screen can display. For the most expensive models of LCD tvs and Plasmas tvs the manufacturers are now claiming to have colour gamuts very close to the full spectrum. Again on a like for like basis the Plasma tvs still out perform the LCD tvs on all but the most expensive models. This is because on cheaper LCD tv models the colour gamut isn’t as good as the top LCD tv models from the same manufacturer. Whereas for Plasma tvs the difference isn’t as great.

Screen Resolution

This can be defined as the amount of information shown on a screen. The more information that is on a screen the higher the quality of the image. The higher resolution usually means that the screen can display a higher quality image with more detail and sharpness. The resolution is measure in pixels. LCD HDTVs and Plasma HDTVs (High Definition Televisions) have a resolution of 1920 pixels x 1080 pixels or 1080P. Where ’1080′ is the vertical resolution and ‘P’ is progressive scan meaning that the image isn’t interlaced. Usually LCD HDTVs are cheaper than the same sized Plasma’s. HD plasma are available in sizes of 42 inches upwards whereas LCD HDTVs are available from 32 inches upwards. Therefore at sizes 32 inches to 37 inches LCD tvs have the advantage of offering 1080P HD compared to the 720P (1280 pixels x720 pixels) HD Ready Plasma tvs. At sizes less than 32 inches there aren’t any plasma tv models.

Response Time and Refresh Rate

These two attributes in combination determine how fast a moving picture a screen can reproduces without the image blurring. Response time is a gauge of how rapidly 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 mostly 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 of the screen

Pictures on plasma TVs are still clearly viewable at about 160 degrees and on some models up to 180 degrees. However the picture dulls further than about 100 degrees.

The screen surface of lcd tvs and plasma tvs

LCD tv screens are available with matt finish screens which lessen glare whereas Plasma tvs have a reflective screen.

Burn-in

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.

Image retention

Numerous people mix up burn-in with image retention which is very similar. With image retention the ‘ghost image’ disappears quickly either when a new, bright image is displayed or after a few seconds. image retention is rarely noticed but normal on plasma tvs because of the technology used, but it can be minimised by having a ‘break-in’ period as soon as the plasma tv is first bought. The break-in period as a rule lasts 100 hours, throughout this time you should not view any programs that do not fill in the whole screen, and you should notview any programsthat have still images such as bright station logos or news scrolls at the base of screens, and you should decrease the contrast and brightness to a middle point. Nowadays there are also features built in to the plasma tvs to lower the possibility of either burn-in or image retention.

How does the Power consumption of LCD tv and Plasma tv compare ?

LCD tvs have a backlight that is alwayson and uses almost constant power. LCD tvs usually have an adjustable back light which uses additional power when it is on a high setting and less on a low setting. The power necessary to modulate the pixels is infinitesimal.

Because Plasma TVs charge the gas in the individual pixels to a plasma to create the light, and the more light that is required on a scene the more energy is used. So pictures with low brightness in them use less energy, and high brightness more energy i.e. the power consumption varies.

On paper it might appear that the Plasma tvs employ a lot more power than LCD tvs. Plasma tv manufacturers tend to quote the maximum power usage at full brightness. But the plasma tvs power power consumption varies 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 identical sized plasma tv is really lower than LCD tv. However if lots of cartoons and sport are viewed then the LCD tv uses less power. So 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.

Life expectancy

Many ‘experts’ claim that plasma tvs don’t last very long. But in reality manufactures are publishing life expectancy figures of 100000 hours, this equates to 11.5 years of non stop use. Clearly there is no reason for concern.

Conclusion – which is the best?

Plasma televisions and LCD televisions both have advantages and disadvantages. LCD tvs have higher brightness, no concerns about screen burn, and they are thinner and lighter. But Plasma tvs have a better real world picture with a higher contrast, blacker blacks, and more natural colours than LCD tvs. Obviously not all Plasma tvs are better than all LCD tvs. A top specification LCD tv will out perform a cheap plasma tv. If you weigh up the advantages and disadvantages a good plasma tv is the best option but you do get what you pay for.