Plasma vs. LCD vs. LED TV
Which TV display technology performs best during use?
Comparative Guide (2): Functional Considerations
In this final part of our plasma vs. LCD vs. LED TV discussion, we discuss how choosing one TV display technology over another may impact the end functionality of a flat-screen television during use. In other words, which TV technology is right for your use?
To answer this important question, one has to see if there are any major differences between plasma and LCD/LED TVs when it comes to issues like image retention, computer use, lifetime, bad-pixels, response time, and power requirements.
We look at each of these aspects to discover more how these display technologies differ—if at all—in these respects
Image Retention: Screen Burn-In and Image-Sticking
In this plasma vs. LCD HDTV debate, screen burn-in is probably the most debated topic by those in favor of LCD and LED TVs.
Yet, while many are aware of burn-in in plasma TVs, few realize that LCD and LED TVs have their own problems as well: they suffer from 'image sticking'. Image sticking and burn-in yields practically the same visual effect on the display panel but the two phenomena are completely different in their nature.
As with all phosphor-based screens, plasma displays are subject to burn-in. 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.
More specifically, burn-in is the result of a damaged pixel (or group of pixels) whose phosphor has been prematurely aged, and therefore glows less intensely than that of surrounding pixels.
The tendency to burn-in varies from brand to brand but in general, plasma screens are more prone to permanent burn-in during their first 200 hours of use. The reason is that fresh phosphors burn more intensely as they are ignited during this period.
The presence of a static bright image for more than 30 minutes may be enough to cause temporary burn-in - often referred to as image retention or image ghosting. Temporary burn-in or image ghosting should not be cause for alarm, as normally this will wash out after several hours of use. In addition, most plasma TVs today come with 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 4:3 content 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 surrounding pixels.
Recent improvements in plasma display technology have certainly extended the time it takes to burn-in a plasma pixel. The use of improved phosphor material, and motion adaptive/pixel orbiting preventive burn-in technology has greatly reduced the risk of burn-in. Rather, 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.
Admittedly, the latest brighter yet more energy efficient plasma panels appear to be more prone to image retention during initial use due to the use of more sensitive phosphors. But as stated, image retention is a temporary state that will become less of an issue with use. In addition, it is easily removed through the use of the provided image retention remedies that come with plasma HDTV.
Worth taking note that keeping brightness and contrast levels close to the lower end of the scale especially during the first 200 hours of use, 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 the latter case, an LCD or LED TV may be a better choice since these are 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.
LCD (both CCFL and LED) TVs do not suffer from burn-in but under certain conditions, they may suffer from image sticking; this is 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 LCD panels and 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 intensity of image retention in LCDs varies among different brands and 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. The good news is that image sticking in LCDs is quite rare in the home environment. More information on image sticking is available in our article: Image Sticking in LCD Televisions.
Plasma vs. LCD vs. LED Image Retention ADVANTAGE:
LCD and LED TVs enjoy a technological advantage; they are not prone to burn-in; in addition, image sticking in LCDs is often completely reversible.
At the same time, 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 habits. Similarly, image sticking with LCD TVs is unlikely to take place under normal home use.
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Both the closer pixel built-up structure of LCDs and LED TVs referred to in our second part of this plasma vs. LCD discussion, and the burn-in issue of plasma panels just discussed above, render LCD (CCFL and LED type) display panels more suitable for computer use. In particular, the pixel build-up structure in an LCD panel makes LCD monitors especially good at displaying large amounts of data even at the sub-40-inch category 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 vs. LEDs - 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.
Earlier plasma displays had a quoted half-lifetime of 20,000hrs, following which the image brightness is expected to fall to half its original value. However, the latest generation plasma displays boast of a quoted panel life of 100,000hrs. The latest LCD displays also have an expected panel life of 60,000 to 100,000hrs. It is true that quoted panel lifetime figures by manufacturers tend to be somewhat inflated, but these figures still 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 just over 7hrs a day. Furthermore, on average, a TV set is replaced every 7 years. Taking a conservative figure of 40,000 hours half-lifetime for either technology, this works out to almost 15 years of daily use before these display panels would ever need replacement.
In other words, lifetime is not an issue when comparing plasma vs. LCD and LED display technologies. At the same time, keep in mind that there is no way to regenerate the gases in a plasma display, nor it is possible 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.
Note that expected panel life is not the same as the expected lifetime of the whole HDTV set. Expected life of the electronics inside an HDTV set is the same as that of other consumer electronics and depends on various factors, including operating ambient temperature and stability of the supply voltage.
Plasma vs. LCD vs. LED - Lifetime ADVANTAGE:
This is a non-issue - rather it is more dependent upon manufacturer quality than display technology.
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. However, with plasma displays, 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.
The issue of bad pixels within the context of plasma vs. LCD TVs mainly arises with CCFL and LED 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 vs. LED - Bad Pixels ADVANTAGE:
Plasma - because even though some LCD manufactures are offering a zero bad-pixel policy, CCFL and LED LCD displays still have a higher tendency of developing bad pixels during use than plasma display panels.
Blurring, Response Time and Fast-moving Images
Response time of LCD HDTV sets is surely among the latest battlegrounds between display manufactures, with the fastest figure quoted so far by LCD TV makers being 1msec for selected flagship LED TVs. However, the de facto standard appears to be 4msec for 120Hz LCD TVs and 2msec for 240Hz LCD HDTVs; these response times are necessary to support the respective refresh rate, in others words to enable all pixels to change their state well in time for the next refresh cycle.
Yet, even 1msec response time is not fast enough in comparison to the minute fraction of a millisecond it takes to ignite the phosphor of a plasma display cell. For this reason, this plasma vs. LCD response time debate is often a hot topic with those in favor of plasma televisions.
For a detailed discussion on this subject, we suggest to refer to our article on LCD Motion Blur. However, for those who would like to go for the short answer, we say that as things stand today, plasma TVs still have an edge in this plasma vs. LCD technology war due to their superior performance during fast action movies, sports and gaming events.
Plasma vs. LCD vs. LED TV: Response Time ADVANTAGE:
Plasma - because even though LCD technology has improved to the extent that this is becoming less of an issue, LCD technology has still some way to go to achieve the same level of pixel response as phosphor-based displays.
Panel Display Noise
An issue that often crops up with those in favor of LCD in this ongoing plasma vs. LCD vs. LED debate is plasma panel noise. CCFL and LED LCD TVs do not suffer from this phenomenon. Buzzing in plasma panels is normal but the level of buzzing is generally quite low and inaudible from normal viewing distance especially at daytime. In most cases, you will have to sit insanely close to your TV to hear it.
This soft buzzing noise is mainly caused by the electrical charges used to create the images on the screen. Buzzing can also result from the high frequency power drive coils in the switch-mode power supply (SMPS) board used to drive the panel.
There are many factors that can influence this plasma display panel phenomenon. For example changing the picture mode from say dynamic to a lower power one such as cinema/movie will also reduce the level of perceived noise since this affects how much power the panel is processing and the power levels processed by the SMPS board. This also explains why the perceived buzz noise changes with picture content - a bright overall scene or a too high contrast setting can generate a more audible noise level. Operating the panel at a high altitude also make plasmas more prone to audible buzzing.
Equally important is panel installation; a hard wall surface directly behind a wall mounted plasma TV will also serve as a more effective reflector than say walls that are covered in softer finishes.
Plasma vs. LCD vs. LED - Display Panel Noise ADVANTAGE:
LCD and LED TVs - even though the level of buzzing noise in plasma is exceptional low. Still, if you are after super quite operation at very close viewing distances and extended use with the volume turned off, like in applications where the TV is also serving as a big PC monitor, then LCDs offer a better option.
Up to a year ago, this was one of those few issues in this plasma vs. LCD TV analysis where LCD TV sets enjoyed a clear-cut advantage. However, the latest energy efficient plasma display panels have significantly reduced the LCD power advantage. These new plasma panels consume some 40% less power than previous generation panels for the same brightness levels.
LCDs still have an advantage in this area; this arises out of the way LCDs use a backlight source to produce images. Backlighting of a display panel to light an image requires less power than to light the individual cells forming the image in a plasma display.
Another major difference between plasma and LCD technology is that plasma displays require more power both with increase in pixel count - i.e. 1080p plasma displays use more power to operate than equivalent screen size 720p plasma sets, and also to display brighter objects. On the other hand, CCFL-LCD panels generally require some minimal additional power when handling large areas of dark subjects over a bright background; 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.
However, actual power requirement in LCDs depend is mainly on the technology used for the backlight. LCD panels using a CCFL backlight system require typically 30% less power than 1080p plasma displays of the same screen size and 20% less power than equivalent size 720p plasma displays.
This difference in power requirement between the two display technologies becomes more pronounced as one moves towards the larger end of the scale, i.e. 55-inch and above. In addition, LCDs using LED backlights are even more energy efficient than CCFL LCDs, with edge-lit LED TVs using less power than LED TVs using full LED array local dimming technology. In fact, edge-lit LED TVs use typically 50% less power than corresponding plasma TVs.
Worth taking note that it is possible to reduce the power requirements of an HDTV irrespective of display technology, by simply applying the correct settings for the contrast and brightness levels to better suit your home environment; actual savings are brand dependent but the energy savings resulting from proper calibration may very well approach 40% over the typical 'Dynamic' out-of-the-box setting.
If energy efficiency is really a priority, you have to 'watch' also your TV viewing habits. I suggest you check the following Energy Efficient TV article at www.Green-Energy-Efficient-Home.com for some interesting tips on how you can cut your energy bill by choosing more efficient habits.
Plasma vs. LCD vs. LED TV Power Requirements ADVANTAGE:
LCD and in particular LED LCD TVs - because despite that the latest plasma display panels are significantly more energy efficient than previous generations, the use of a common backlight source in LCDs is inherently more efficient than lighting the individual pixels in the light cell-structure forming a plasma display.