A Plasma HDTV or a LCD Television – Is this your dilemma? This is a rather difficult and complicated comparison between two technologies that process the image in a totally different manner. This article highlights the pros and cons of plasma versus LCD as applicable to a television display. It also presents a set of guidelines to help you determine where either of these two flat panel display technologies fit best.

Plasma or LCD – Which type of display is right for you?
Though both LCD and plasma displays come in the form of slim flat panel displays, yet from a technology perspective, these two flat panel displays process the image in a totally different manner. Plasma uses a matrix of tiny gas plasma cells that are charged by precise electrical voltages to emit light and hence to create the picture image. Liquid Crystal Displays (LCD) panels - work by trapping a liquid crystal solution between two sheets of polarized glass. When an electric current is passed through the liquid crystals, they change the polarization of the light passing through them in response to the electric voltage – as a result of which, more or less light is able to pass through the polarized glass on the face of the display. It is not the scope of this article to go into the actual details of how these different display technologies process the image – after all, what really matters is not what is going behind the screen but rather how these different display technologies perform as a television screen. At the same time, it is worth taking note that it is these same differences that gives each of these display technologies, its strengths and weaknesses, and that therefore renders one more suitable than the other in certain circumstances. The list below highlights the most important differences between these two flat panel display technologies:

Size:
For the time being, collision between plasma television and LCD TV occur in the 40 to 50 inch screen range. In reality, LCD TVs top out at around 45” – meaning that for bigger screen sizes, a plasma display is your only real option if what you are after is a direct-view TV system. On the other hand, at the smaller end of spectrum, namely 15” to 36” TVs, LCD is the way to go if what you want is something stylish and slim (at under 4-inches in depth).

Picture Quality, Contrast and Color Saturation:
Both plasma and the latest TFT-LCD flat panel displays are capable of producing excellent picture quality – with bright, crisp clear images. However, plasma flat panel displays are more suitable for basic home theater usage than LCD. The gas cell structure within a plasma display is such that there is no light leaking between adjacent cells (or pixels). This renders plasma displays capable of displaying deeper blacks – hence better contrast and detail in television and movie scenes where lots of dark and light content is shown simultaneously. In comparison, the nature of LCD technology – where a backlight shines through the LCD layer – means that it is hard for it to achieve true blacks (i.e. true absence of light) as there is always some light leakage from adjacent pixels. This does not mean that LCD panel s are not suitable as TV screens; today’s LCD TV sets make use of extreme high contrast panels that are capable of displaying deeper blacks, yet the latest plasma TV sets still have a slight edge over LCD when it comes to contrast levels. The situation is somewhat similar when it comes to color saturation. Again, it is the different display structure between LCD and plasma that is the reason behind the difference between the two technologies in this respect, and though both are capable of handling color in an exceptional manner, yet plasma displays still lead in this respect - producing more accurate and vibrant colors.

Viewing-angle:
Plasma Television sets – like their CRT TV counterpart - typically have better viewing angles than LCD. The viewing angle represents how far one can sit on either side of the screen away from the center, without experiencing significant deterioration in picture quality – mainly as a result of color shifts and reduced contrast. Though recent developments in LCD technology means that this is less of an issue with some of the latest LCD TV sets boosting a viewing angle of 160 to 170 degrees vertically and horizontally, yet it is always best to check. The tendency – especially with cheaper sets – is that the deterioration in picture quality is more accentuated with LCD than with plasma displays.

Burn-In:
As with all phosphor-based displays, plasma displays are prone to burn-in, or image retention. Screen burn-in occurs when an image is left for too long on the screen – resulting in a ghost of the image burned on the screen. Surely, keeping the brightness and contrast levels down will help reduce the risk of burn-in. While some brands of plasma displays are more prone than others to burn-in, yet in general, plasma screens are more prone to suffer permanent burn-in during their first 200 hours of use; the reason being that fresh phosphors burn more intensely as they are ignited. Technically speaking, burn-in is the result of a damaged pixel, whose phosphors has been prematurely aged and therefore glows less intensely than those of surrounding pixels. The presence of a static image for more than half-an-hour is enough to cause temporary burn-in; temporary burn-in or image ghosting, should not be cause for alarm as normally this will wash out after several hours of use. Worst still is the prolonged presentation of static displays, such as the use of black or gray bars to view a 4:3 picture in its original format on a wide screen display; this will result in a permanent burn-in. Once permanent burn-in occurs, the damaged phosphors cannot produce the same levels of light output as the other phosphors around them do. In these circumstances, an LCD display may be a better choice.

Viewing distance:
It seems that the pixel size and shape of an LCD panel renders a smoother picture than an equivalently sized plasma panel for the same pixel count. This means that even if your viewing distance falls within the recommended distance of approximately twice the screen width, if this is less than at least nine feet, most probably you will be better off with an LCD TV.

Life-time:
The rare gases used in plasma display panels have a life and will fade over use. Earlier plasma TV sets had a quoted half-lifetime of between 20,000hrs, following which the image brightness will fall to half its original value. However, the latest plasma displays can boost anything between 30,000 and 60,000 hours. On the other hand, LCD displays have a guaranteed lifetime of between 50,000hrs and 60,000 hours. This degradation in image brightness takes place gradually over time. Now, the average household in the US replaces their TV set every 7 years. Taking a conservative figure of 30,000 hours for either technology, this corresponds to well over 6hrs usage a day - every day - for over a period of 14 years! In other words, both plasma and LCD displays are extremely stable and reliable devices. This means that life-time should not be an issue with either display technology. At the same time, keep in mind that there is no way to re-generate the gases in a plasma display or to repair any ‘dead’ pixels in an LCD display – the only option in such circumstances will be to replace the display.

Response:
Some LCD panels – especially on older generation models - had a tendency to blur images particularly during fast moving scenes in movies and sports. However, recent advancement in LCD technology means that response times are such that there is no noticeable difference in performance between LCD and plasma TV sets in this regard.

Power requirements:
The advantage here goes to LCD panels as these consume less electricity. Estimates show that the use of LCD panels can result in some 30% power savings for the same screen size than plasma display.

Price:
Price is always a big issue when it comes to choosing your TV display. Although prices online vary considerably, yet LCD TV sets tend to be more expensive than Plasma Televisions. The main reason behind this price gap is that the production process for plasma technology still supports a better yield and thus carries a pricing advantage – especially at the large screen end of the market. This contrasts heavily with LCD display technology where an estimate 30 to 40 per cent of all manufactured panels will have to be discarded as a result of defects leading to what are known as 'bad-pixels'.

Making the Choice:
There is a market for both plasma and LCD displays - Plasma gives you a bigger screen for your dollar, deeper blacks, but then LCD do not suffer from burn-in and at the smaller end of the market (less than 40-inch screen size), LCD is your only way forward if you want something slim and stylish. It is all a question of knowing what are the advantages and limitations of each with respect to your specific needs.

Andrew Ghigo is Editor & publisher of www.practical- home-theater-guide.com - a comprehensive home theater guide to home theater systems, product reviews and home theater design.