Plasma vs LCD TV - A Detailed Comparative Guide (3): Functional Considerations

In this final part of our plasma vs LCD TV analysis, we discuss how choosing either technology impacts the end functionality of a flat-screen television.

Plasma vs LCD: Functional Related Issues

Are there any major differences between these two different flat-panel TV technologies when it comes to issues like image retention, computer use, lifetime, bad-pixels, response time, and power requirements?

In this part of our plasma vs LCD debate, we look at each of these aspects to discover more how plasma televisions and LCD TVs differ - if at all - in these respects

Image Retention: Screen Burn-In and Image-Sticking

When it comes to comparing plasma vs LCD TV sets, screen burn-in is probably one of the most debated topics by those in favor of LCD display technology.

Yet, while many are aware of the susceptibility of plasmas to burn-in, few realize that even LCD TVs have their own problems - they suffer from a phenomena known as 'image sticking'.

Though image sticking and burn-in yields practically the same visual impact on the display panel, yet these two phenomena are completely different in their nature.

Burn-in

As with all phosphor-based screens, plasma displays are prone to burn-in. Screen burn-in is a form of image retention and occurs when an image is left for too long on the screen. This results in a ghost of the image burned on the screen.

Keeping the brightness and contrast levels down, especially during the first 100 or 200 hours of use will help reduce the risk of burn-in.

While some brands of plasma TV sets 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 is that fresh phosphors burn more intensely as they are ignited.

Burn-in is the result of a damaged pixel whose phosphor has been prematurely aged, and therefore glows less intensely than those of surrounding pixels.

The presence of a static image for more than 30 minutes may be 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. Some models have built-in features to remove image ghosting once this occurs.

More preoccupying with plasma displays is the prolonged presentation of black or gray bars, say when viewing a 4:3 picture in its original format on a wide-screen display. This may easily lead to permanent burn-in. Once permanent burn-in occurs, the damaged phosphors in a pixel cannot produce the same levels of light as that of the surrounding pixels.

Recent improvements in plasma display technology have certainly extended the time it takes to burn in a plasma pixel cell. The use of improved phosphor material, and motion adaptive/pixel orbiting anti burn-in technology has greatly reduced the risk of burn-in. It has got so much better that in our opinion, persons with normal viewing habits have nothing to worry about, especially after the first 200 hours of use.

Still, keeping brightness and contrast levels close to the lower end of the scale would help reduce any potential burn-in risks, especially if the application calls for part of the image on the screen to remain static during use.

In these circumstances, an LCD TV may be a better choice since LCD technology is not prone to screen 'burn-in'. In other words, no premature aging of cells occurs in an LCD TV panel due to the prolonged presence of a static image.

Image Sticking:

Still, LCD displays do suffer from image sticking - a form of image retention that yields similar visual results to burn-in in plasma TVs. The main LCD advantage here is that unlike burn-in, image sticking can often be reversed to the point of total invisibility.

Image sticking is an intrinsic behavior of TFT LCD panels. It can occur when a static image remains displayed on the screen for an extended period as a result of a parasitic charge build-up within individual pixels. This 'retained pixel charge' will prevent the liquid crystals to return fully to their 'relaxed' state upon removal of the static image.

The result is a faint, visible, retained image that remains on the screen even when the image is changed. The intensity of image retention varies among different brands. It also depends on several factors including operating temperature, image make-up, and time the static image remained on. Similarly, the level of reversing image sticking depends on the causes that led to image retention on the LCD panel.

More information on image sticking, including ways to reverse it and how best to avoid it, is available in our article: Image Sticking in LCD Televisions.

Plasma vs LCD - Image Retention ADVANTAGE:

LCD TVs enjoys a technological advantage; they are not prone to burn-in, and image sticking in LCDs is often completely reversible, but...

Burn-in is no longer much of a concern as it used to be with plasma televisions up to the recent past, especially for persons with normal TV viewing requirements. Similarly, image sticking with LCD TVs is unlikely to take place under normal home entertainment use.

Computer Use

Both the closer pixel built-up structure of an LCD referred to in our second part of this plasma vs LCD discussion, and the burn-in issue of plasma panels just discussed above, help render LCD displays more suitable for computer use.

In particular, the higher number of pixels per square inch on an LCD panel makes LCD monitors especially good at displaying large amounts of data with exceptional clarity and precision. It is also for this same reason that LCD panels tend to perform better in applications like video gaming.

Plasma vs LCD - Computer Use ADVANTAGE:

LCD, partly, because of their non-susceptibility to burn-in, and partly as a result of their ability to display detailed graphics better.

Life-time

The rare gases used in plasma display panels have a life-time and will fade gradually over use. Earlier plasma displays had a quoted half-lifetime of 20,000hrs, following which the image brightness will fall to half its original value. However, the latest generation of plasma displays boosts a quoted half-lifetime of 60,000hrs. Similarly, LCD displays have an expected quoted half-lifetime of between 50,000hrs and 60,000hrs. It is true that quoted half-lifetime figures by manufacturers tend to be somewhat inflated, but still these figures contrast heavily with the typical 20,000hrs half-lifetime for direct-view CRT TV sets.

But what do these half-lifetime figures imply? Statistics show that TVs in an average US household remain on for over 7.5hrs a day. Furthermore, on average, a TV set is replaced every 7 years. Taking a conservative figure of 30,000 hours half-lifetime for either technology, this works out to well over 10 years of daily use before these flat-panel TV sets would need replacement.

It is thus clear that lifetime is not an issue when it comes to comparing plasma vs LCD display technology.

At the same time, keep in mind that there is no way to regenerate the gases in a plasma display. Similarly, it is impossible to repair any ‘dead’ pixels that may develop during use in an LCD panel. The only option in these circumstances will be to replace the display.

Plasma vs LCD - Lifetime ADVANTAGE:

This is a non-issue with either technology - rather it is more dependent upon manufacturer quality.

Bad Pixels

Both plasma and LCD displays may suffer from bad pixels - at times also referred to as 'stuck' or 'dead' pixels. In other words, both technologies may develop defective pixels during the manufacturing process even though in a plasma display, bad pixels are rare.

The interesting thing here is that some manufactures are moving towards a 'zero' bad pixel policy. This means that they will replace your flat-panel TV within (typically) 6 months from the date of purchase, should it develop even just one single bad pixel during this initial period of use.

However, the issue of bad pixels within the context of plasma vs LCD mainly arises with LCD TVs. The reason is that even if on day one, you have a perfect LCD display, the switching transistors associated with the pixels and sub-pixels in an LCD panel may still get faulty at some point later in use.

Plasma vs LCD - Bad Pixels ADVANTAGE:

Plasma - because even though some manufactures are offering a zero bad-pixel policy, yet LCD displays still have a higher tendency (with respect to plasma panels), of developing bad pixels during use.

Response Time and Fast-moving Images

Response time of LCD HDTV sets is surely among the latest battlegrounds between display manufactures. The present de facto standard appears to be the 8msec for LCD panels, though some LCD display manufactures have stated to quote response figures as low as 4msec and even 2msec!

But even 2msec is more than what plasma can achieve. For this reason, this response time debate is one of those hot topics with those in favor of plasma televisions when comparing plasma vs LCD TVs.

For a detailed discussion on this subject, we suggest that you look at our article on LCD Response Time. However, for those who would like to go for the short answer, we still say that:

As things stand today, when comparing the pixel response times of plasma vs LCD TV sets, plasma TVs still have a slight edge in performance during fast action movies, sports and gaming events.

Plasma vs LCD - Response Time ADVANTAGE:

Plasma - because even though LCD technology have improved to the extent that this is becoming less of an issue, yet LCD technology has still some way to go to achieve the same pixel response level as phosphor based displays.

Power Requirements

This is one of those few issues in this plasma vs LCD TV analysis where LCD TV sets enjoy a clear-cut advantage. However, the extent of this advantage varies with the screen size and diminishes to the point of almost insignificance as one approaches the smaller end of the scale where the two technologies collide, namely 32-inch.

There is a very simple reason for this. LCD panels use a backlight to produce images that requires substantially less power to operate than the plasma 'cell-based' display structure. The use of a backlight in LCD panels contrasts heavily with plasmas, which do require substantial power to light each pixel forming the display.

Another major difference between plasma and LCD technology is that plasma displays require more power when handling bright subjects. On the other hand, LCD panels require more power when handling dark subjects. This in view that for an LCD display to present a dark subject, more pixels will have to be activated to block more of the light produced by the backlight source from reaching the display surface.

This backlight issue has a further implication. The actual power requirements of LCD displays depend mainly on the technology used for the backlight. In general, LCD panels using standard CCFL-based backlight systems require typically 30% to close to 50% less power than plasma displays of the same screen size; the difference being more pronounced as one moves towards the larger end of the scale - 57" and above.

LED backlit LCDs are even more energy efficient - requiring significantly less than half the power of a similar size plasma HDTV. The recently released Samsung LN46A950 LED backlit LCD requires less than 56% in terms of watts/sq. inch than the Samsung PN50A650 plasma HDTV. Comparing power in watts per sq. inch is important as here we are dealing with displays of a different size.

At the smaller screen sizes, things are different. When comparing plasma vs LCD sets at the 37-inch and 32-inch, the use of a common backlight as used in LCD displays does not result in any noticeable advantage over similar size plasma TVs. Rather, here the power requirements are highly dependent on the electronics used to drive the display than on the display panel itself; this in itself is extremely brand dependent. In fact, as indicated in the comparative table below, while the Sony LCD uses around 8% less power than the Vizio plasma HDTV, the Samsung LCD uses some 4% more power than the plasma featured in the list.

Worth taking note that it is possible to reduce the power requirements of an LCD TV or a plasma television by simply applying the correct settings for the contrast and brightness levels to better suit your home environment. Again, the actual savings are highly brand dependent but the energy savings resulting from proper calibration may very well approach 40%.

Plasma vs LCD - Power Requirements Comparative Analysis: The table below depicts the actual power requirements for the selected LCD TVs and plasma television sets:

Technology	Size	Model	Default Power (Watts)	Watts/Sq. Inch
LCD	52-inch	Samsung LN52A650 - 1080p	220	0.19
Plasma	50-inch	Samsung PN50A650 - 1080p	380	0.36

LCD	46-inch	Samsung LN46A950 - LED 1080p	146	0.16

LCD	32-inch	Sony KDL-32M4000 - 720p	113	0.26
LCD	32-inch	Samsung LN32A450 - 720p	131	0.3
Plasma	32-inch	Vizio VP322 - 720p HDTV	123	0.28

Plasma vs LCD - Power Requirements ADVANTAGE:

LCD - because the use of a common backlight source to produce the image proves to be a more efficient way than lighting the individual cells forming a plasma display.

Choosing between a Plasma TV and an LCD Television Plasma vs LCD - a Comparative Guide (3) Functional Considerations