Which is better - LCD or Plasma TV?

 The Plasma vs LCD debate is an important issue to anyone thinking of buying a new TV.  We present the following information in order to help you to make a decision and hope that with our qualifications and experience we can guide you through the process, highlighting the main areas that you need to consider before you commit to a purchase.

 LCD / Plasma television comparisons

The two technologies are very different and a little understanding of how the display works will help you to understand why the pictures have different qualities. The technology behind the screen is just one part of the process that goes to form the overall picture as behind each display (literally) is a wealth of picture processing backed by years of research and continuing development that makes improvements in picture quality with every new model. This continuous development also means that old comparisons between plasma and LCD televisions, even those made only a year ago, may not be relevant any more.

 So what do you need to consider in order to answer the plasma vs LCD question? The main questions to answer are:

Does screen burn exist?
How does the picture quality compare?
What screen sizes are available?
Does the power consumption differ between the formats?
How long do they last?

We will look at each of these in turn below but first a look at how the picture is produced on the screen of each format.

What is the difference between LCD and Plasma TV Technology

 Both technologies rely on the use of red, green and blue primary colours. By mixing these three colours together in varying intensities any colour can be reproduced in much the same way as colours were reproduced in cathode ray tubes in the good old days. The individual red, green or blue colours are known as sub-pixels; collectively all three colours make up a single pixel. A full HD display requires 1,920 pixels horizontally and 1,080 pixels vertically.

How does plasma TV work

 Plasma display panels rely on electrodes to cause the excitation of various gases such as xenon, neon and argon held within each sub-pixel. These gases emit ultra-violet photons that in turn excite red, green or blue phosphors coated onto each sub-pixel.

 By controlling the charge sent to each sub-pixel by the electrodes, each pixel can be made to appear as any one of millions of colours. As it is produced by glowing phosphors, the type of light emitted from a plasma screen is very similar to that which was produced by a cathode ray tube.

                                                                                               image source - wikipedia

LCD displays, on the other hand, are quite different. The display relies on a backlight to illuminate coloured filters placed behind each sub-pixel. Liquid crystals can be made to become opaque and block the passage of this coloured light, or they can be made to allow the light to pass through to the front of the screen, depending upon the electrical charge applied to each sub-pixel. The combination of the colour and intensity of the three sub-pixels makes up the apparent colour of each pixel on the screen.

                                                                                          image source - wikipedia

 The technology behind the two types of display explains the difference in the quality of light and colours that plasma and LCD televisions produce and no amount of digital processing can change the inherent nature of these technologies – they will always produce a different kind of image.

Does Screen Burn Exist?

This is the most significant issue concerning most people when considering LCD vs plasma.

 Plasma TVs use phosphor to generate light as is the case in cathode ray tubes. Over time the phosphor coating loses its ability to emit light and the brightness gradually falls away – not drastically though, manufacturers quote time periods approaching 10 years before the brightness halves.

 The problems occur when this happens more on one part of the screen than the rest. Displaying fixed images such as TV channel logos or computer graphics can cause parts of the screen to age faster than the rest, eventually resulting in permanently reduced brightness in those areas. This is especially so during the first two hundred hours or so of the TVs life when luminance falls off relatively quickly as components bed in.

 Manufacturers have developed systems for the prevention of screen burn by constantly moving the image around the screen slightly but this should not be relied upon. Once screen burn is obvious it is probably permanent and some manufacturers will not rectify this problem under warranty.

 A lesser problem that is often confused with screen burn is image retention. This is where a part of the picture has been displaying a bright image for a period of time and this can result in an electrical charge building up on those pixels. This phenomenon is not permanent and the effect will either disappear in time of its own accord or it can be helped along the way by various screen wash programs built into the TV.

 Screen burn does exist in plasma TVs, but in our view it is relatively easy to avoid and we do not believe that this should not put you off the format altogether. LCD TVs do not suffer from screen burn.

How Does the Picture Quality Compare

 LCD televisions have traditionally had difficulty displaying true blacks. The standard LCD technology incorporates a backlight which is permanently switched on and this tended to allow some bleed-through even when the pixels were intended to be opaque. Several years ago this was a major problem and blacks were displayed as a shade of grey, but significant improvements have now been made in this area even where the same basic technology is in use. By comparison, Plasma TVs are inherently much better at displaying blacks and yet they too continue to improve in this area.

The ability to display bright whites and deep blacks is known as contrast ratio (the higher the ratio, the better), but be aware that some manufacturers have methods of measuring this which do not reflect the true performance in normal viewing conditions.

 The backlight technology can be an advantage in certain circumstances. The bright, vibrant picture as displayed on LCD televisions in high street shops may appeal if you are looking for a TV for the kitchen, where your lights may be almost as bright as in the shops, or for gaming perhaps, again in well lit rooms. Conversely, that same vibrancy may not be appropriate for a dimly lit lounge or home cinema. In these instances, plasma may well have the edge. Plasma displays can produce a far more subtle image with good colour reproduction and deep blacks and they traditionally have been the display of choice for the video-phile and the home cinema purist (when the projector is not in use of course).

 Another area where plasma has traditionally scored highly is in the reproduction of scenes containing fast motion. This ability of a plasma display to turn pixels on and off quickly has always been good and is now comparable to the old cathode ray tubes. In the past, LCDs have generally had much poorer response times, though these are rapidly catching up to the extent that the once-common smearing effect has now virtually gone completely and will be difficult to spot. Try to view sports or fast moving scenes on the TVs in your shortlist to confirm this.

 Viewing angle was once a problem for LCD screens, where the picture quality would drop off as the angle between the viewer and the screen became more acute. Manufacturers are quoting viewing angles of 178 degrees for current screens. Check this out if you have so many friends that they need to sit at such extreme angles, but they are more likely to leave because of where you have made them sit than because of the picture quality!

What Screen Sizes are Available?

The old rule stating that LCD panels were small and plasma panels were large no longer really applies, although plasma does not appear in very small sizes. Typical sizes offered by current suppliers range from 19” to 52” for LCD and 37” to 65” for plasma. In fact there now appears to be a competition between manufacturers to produce the largest panel with both formats being available (to those with very deep pockets) in sizes exceeding 100”.

 Producing a full HD plasma panel of 42” or less has proved difficult, but production techniques have now improved to the extent that all the required pixels and their associated electronics can fit comfortably into these ‘smaller’ screen sizes.

How Does Power Consumption Compare?

 At one time it was clear that LCD TVs consumed the least power and plasma TVs were noted for their outrageous running costs. Now the differences are much less obvious and a number of models in both formats have been accepted as meeting the high standards of the Energy Saving Trust.

 The comparison is complicated by the fact that LCD TVs consume most of their power illuminating the backlight which remains on permanently. Plasma TVs on the other hand consume less power when displaying a dark scene than when displaying a bright scene, so a quick glance at the specifications in the user manual will not reveal the true power consumption in normal use. Some manufacturers now quote an average power consumption figure and this is the better figure to use for a direct comparison between LCD and plasma TVs.

 It is fair to say that there is very little difference in real terms between the two formats and the difference is more down to user settings than the type of TV. If power consumption is important to you, turn down the ambient lighting and adjust your TV accordingly, then you’ll save power lighting the room and running the TV!

 One important point to note if you are unable or unwilling to turn off your TV completely when not in use, is that the power consumption in standby mode regardless of whether the TV is LCD or plasma, is typically less than 1 watt for current models. This equates to less than 6kWh over a full year, assuming that the TV is in use for 8 hours per day and in stand-by for the rest of the time. Manufacturers have clearly made significant advances in this area in recent times.

How Long Will They Last?

 A common fear surrounding the plasma TV is that the gases within the screen will eventually escape and render the screen useless. This is as likely as the vacuum dispersing in a cathode ray tube. Plasma screens do not need re-gassing. Current manufacturing processes mean that the gases do not escape (though it’s not advisable to use them at very high altitude). Manufacturers of both formats quote lifetimes of 60 000 hours or more - the equivalent of 20 years if used for 8 hours per day.

Summary

 To summarise, virtually all of the disadvantages of both formats have been designed out. At the lower end of the scale, neither plasma nor LCD TVs perform particularly well owing to the fact that the processing electronics have most likely been trimmed to keep the costs down.

 With a limited number of exceptions, a more expensive TV of the same size in either format will out-perform a cheaper TV of the other format, which demonstrates that the final picture has as much or more to do with the picture processing electronics than with the technology behind the screen. So our advice would be to find a TV of the right size for your room with a picture, a design and a price that you like, then check the ticket to see whether it’s LCD or plasma!