Sep 23, Plasma vs LCD TV - A Detailed Comparative Guide (2): Picture Matters

This is one of those areas in this plasma vs LCD TV shoot-out, which is becoming increasingly difficult to determine where to go. This in view that the latest generation plasma and LCD flat panel displays are both capable of producing excellent picture quality – with bright, crisp clear images. Yet there are still a few significant differences when it comes to plasma vs LCD picture performance - including with respect to LED TVs -  that renders one display technology more suitable than the other under certain circumstances.

Plasma TV sets are generally more suitable for home theater use than LCD TVs, even though the latest LED TVs are capable of achieving exceptionally deep blacks.

However, plasma TVs picture quality characteristics render plasma television sets more suitable for use under controlled lighting. The main reason is plasma's deeper blacks. The gas cell structure within a plasma display is such that there is no light leaking between adjacent cells (or pixels). This enables a plasma TV to display deeper blacks than its LCD counterpart especially when handling mixed content images with predominantly dark content but that still contains small bright areas to be displayed simultaneously over the dark background.

Some may argue that LED TVs are also capable of exceptionally dark blacks in comparison to CCFL LCD TVs but take note that even the more precise LED TVs with full array local dimming are not capable of producing the deepest blacks of the best plasmas when handling bright objects over a predominantly dark background.

Improved black level performance is a most important picture quality parameter as it helps render better those difficult-to-define quality attributes like picture depth, scene detail - especially in television and movie scenes where lots of dark and light content is shown simultaneously, and color richness - more specifically the perceived color saturation. Indirectly, a better black level also leads to better rendering of picture contrast.

In comparison, the nature of LCD technology – where a backlight shines through the LCD layer – makes it difficult to achieve true blacks, i.e. true absence of light. There is always some light leakage between adjacent picture elements in an LCD panel. And this applies even to the latest LED-backlit LCD TVs using local dimming technology and especially edge-lit LED TVs. The latter are basically nothing more than CCFL LCD TVs with the CCFL replaced by a LED backlight. While LED TVs can literally switch the LED backlight off to achieve total darkens say between scenes, yet their overall black level performance with mixed content nowhere approaches that of the best plasma TVs.

In fact, the darkest images on a plasma TV can be as dark as a fraction of a candela. This corresponds to the 'brightness' of the turned-off phosphor. In the case of an LCD television, the 'brightness level' of the darkest picture scenes is significantly higher; in the worst case, it can even reach one candela - at times even more, and this when viewed just right in front of the LCD display. View the LCD screen at an angle, and you will find that its black level performance deteriorates significantly. As stated, LED TVs can achieve total darkens by switching the LED backlight off but you cannot take black level on its own; more important than the deepest black a TV can achieve is the overall black level performance with mixed content.

In other words, when it comes to plasma vs LCD, despite the latest improvements in LCD technology - especially with LED TVs, plasma still enjoys a technological advantage.

In general, the color accuracy of LCD panels is still not exactly on par with that of the best plasma televisions - but the difference between high-end models for both display technologies is just a hair apart and often noticeable only under a test environment.

The reason for the slight plasma edge in this respect arise out of the way color is produced in LCD displays where white light from the backlit source is filtered through micro color filters build in sub-pixels.

This LCD light transmissive method of controlling color is an inherently difficult process to maintain color accuracy and vibrancy - even though most LCD displays manage to do quite an impressive job. Instead, plasma generates color direct at the light source - thanks to the different phosphors used in the individual sub-pixel elements.

In general, plasma displays continue to exhibit more richness in color information and more natural coloration; on the other hand, LCD display panels would normally tend towards over-saturation. This over-saturation, together with the inherent anti-glare technology employed in LCD panels, and their relatively brighter image, render LCD panels more suitable for use in brightly lit rooms.

This does not mean that LCD panels are not suitable for use in the home theater. Some of the latest generation LCD HDTV sets make use of intelligent backlight units that are capable of delivering even greater color freedom, thus yielding more true to life colors. In particular, the latest developments in LCD panel backlights using LED light are capable of more accurate rendering of color detail. LED TVs within this category include the Samsung 46-inch UN46C8000 and 55-inch UN55C8000 edge lit LED TVs with precision dimming, and LG 55-inch 55LE8500 and 47-inch 47LE8500 LED TVs with full array local diming backlight technology. These LED TVs are capable of top-notch performance but this superior performance with respect to other LCD TVs does not come cheap.

The latest energy efficient plasma display panels from Samsung, Panasonic, and LG are also capable of producing relatively very bright images despite their lower power consumption levels. This makes these new 2010 plasma TVs also suitable for use in brightly lit environments. Yet we still recommend using LCDs under bright lighting instead of plasma as apart from plasma's higher power consumption levels, prolonged use of high brightness levels in plasma displays may eventually reduce their phosphor lining performance.

And what about contrast ratio? We are seeing some really high contrast ratio ratings for both plasma and LCD TVs - with the latest trend being the popular mega-contrast ratings. The biggest number we have seen so far averaged 5,000,000:1 for most premium plasma TVs and 10,000,000:1 quoted by LG for its latest LX9500 3D LED TV series.

Yet when it comes to comparing plasma vs LCD contrast performance, the real problem with LCD televisions is not insufficient contrast with respect to plasma TVs. Rather, it is the deterioration in picture quality associated with LCDs due to a noticeable lowering in contrast and black levels with off-axis viewing; this also leads to loss of color saturation. This is especially so with LED TVs due to their restricted viewing angle. This is not the case with plasma TVs.

A word of caution here about high contrast ratio ratings: Manufactures like to impress with excessive high figures. However, keep in mind that it is not possible for the human eye to perceive any difference in contrast between a ratio of say 5,000:1 and 10,000:1, even in pitch darkness. There is also the issue that static (at times also referred to as on-screen contrast ratio), and dynamic contrast ratings are not one and the same thing. Manufacturers tend to quote the latter as it yields a bigger number.

Furthermore, the perceived contrast level by the eye depends on a number of factors. Apart from the level of ambient light - which may very well render even a rating of 100:1 academic, in the case of direct-view displays like plasma and LCD, contrast ratio performance is also dependent on the effectiveness of the screen anti-glare filter in maintaining black levels under bright lighting - more specifically in its effectiveness in blocking external light from entering the display panel. For more information on this issue, please refer to our Contrast Ratio article.

Image uniformity encompasses a number of aspects that range from uniformity of the image brightness across the screen to image smoothness. These are issues that are highly dependent on the display technology but quite a few of these uniformity issues may arise out of problems with the video processing itself and therefore, may vary significantly between brands.

When comparing plasma vs LCD image uniformity performance, plasma enjoys a definite edge over LCD TVs. In particular, plasma seems to be more forgiving when displaying noisy video content. In a similar manner, shadow gradations on plasma looks smoother than on an LCD.

Furthermore, problems related to lack of uniformity in the image brightness across the screen are exclusively LCD related. LCDs often exhibit a sort of a brighter spot - how pronounced varies from make to make, but in general, brightness is not 100% uniform across an LCD TV screen - mainly because of problems with the backlight-diffuser system used to spread light across the full display area. And with edge-lit LED TVs, screen uniformity may get even worse than with CCFL LCD TVs. This is not the case with plasma TVs.

Issues such as banding, clouding, and pillaring are all forms of uniformity issues associated with problems in the LCD backlight. These problems may arise with both CCFL-based LCDs and edge-lit LED backlights. Additionally, LED LCDs using local dimming technology may also exhibit a sort of halo effect - also referred to as blooming - when displaying bright objects over a predominantly dark background.

LCD TV with clouding problem

These brightness uniformity issues in LCDs are often further pronounced with off-angle viewing.

3D has taken a much slower start that what TV makers expected but for those interested in 3D TV, it is interesting to note that plasma and LCDs (CCFL and LEDs) does not perform the same.

Again, it is plasma that takes the upper hand here. It seems that unlike plasma TVs, LCD televisions - whether using a CCFL or LED backlight - are more prone to image crosstalk. The latter is a phenomenon in 3D viewing where a subtle washed-out image intended for the right eye appears as a halo around the image intended for the left eye and vice versa.

This affects the 3D image detail - leading to a subtle double image effect that may at times become annoying with some 3D content. In the worst case, it may even cause eye fatigue.

It is true that 3D Crosstalk can be caused by a variety of factors including lack of accuracy in the synchronization between the TV and the shutter glasses, as well as too high contrast TV settings or a high contrast image. But it is also enhanced by an insufficient pixel response time. Even the superfast (for an LCD) 1 msec response time of the LX9500 LG LED TV flagship series is not fast enough to eliminate crosstalk completely. Mind you, the LG flagship faster response time helps reduce 3D crosstalk over slower LCD TVs - including the Samsung C8000 series, but it is still present on this flagship LED LCD TV.

Instead, reviews of the latest 3D Panasonic plasma TVs show that these plasma HDTVs can produce an exceptionally 3D picture with hardly any visible crosstalk.

But the way, LCD panels have another drawback when it comes to 3D TV! Because of the polarizer layer used on LCD panels - both on the TV display and the 3D glasses, the viewer has to sit in an upright position to get the 3D effect; try to tilt or relax and sit back with the glasses at an angle to the LCD screen and the image would go dark as the polarization of the display panel and that of the glasses cross each other.

Here our thumbs up in this plasma vs LCD analysis goes to plasma televisions, even though both technologies are extremely close in terms of overall picture performance, but...

In general, plasma color richness and naturalness will prevail in rooms with low to normal lighting. Plasma also performs better when it comes to 3D TV due to its less susceptibility to 3D image crosstalk. Instead, LCDs will perform better in brightly lit rooms due to their inherent anti-glare technology and higher brightness levels.

We continue this plasma vs LCD discussion by looking at how picture quality behaves with a change in viewing angle.

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 because of color shifts and reduced contrast.

Plasma televisions typically have a better viewing angle than LCD TVs as they hold black levels much better with off-axis viewing than LCDs. This usually occurs at around 100 degrees, i.e. at some 50 degrees on either side of a line drawn normal to the center of the screen.

The main reason for this difference between these two technologies arise out of the fact that each pixel in a plasma display panel produces its own light, rather than light being spread across the screen from one central backlight source and then controlled by active polarized elements in the display panel. Hence, each pixel is more readily visible even when viewing at an angle to the screen surface because its brightness is consistent with every other pixel on the screen.

Recent developments in LCD technology mean that this is less of an issue - rather it is becoming a non-issue especially with the latest generation of CCFL LCD televisions. With LED LCD TVs, the situation is somewhat different; these still suffer from a somewhat restricted viewing angle and unless you take the best seat, you would not enjoy the best picture.

What used to be a clear advantage for plasma displays is becoming more and more a non-issue especially with the latest generation of LCD televisions, however...

Do not always assume that viewing angle is no longer important when comparing plasma vs LCD, especially if the viewing angle is not specified. The tendency – in particular with cheaper LCD TV sets - is that the deterioration in picture quality is more accentuated with LCD and in particular LED TVs, than with plasma displays.

The minimum recommended viewing distance for a 1080p HDTV is approximately twice the screen width. Yet, due to the different pixel structure between plasma and LCDs, if the viewing distance is less than 6 to 8 feet, probably you will be better off with an LCD TV. The pixel size and display build up structure of an LCD panel help render a smoother picture than that from equivalent size plasmas for the same pixel count.

For a detailed discussion on TV viewing distance considerations, we advise to check our article here.

None if you are within normal viewing distance for your screen size; this applies as long as your viewing distance is more than approximately 6 to 8 feet away from the TV screen.

If you have a too short TV viewing distance, an LCD television may render itself better as its pixel structure is less visible.

Up to not long ago, LCD panels used to deliver more in terms of pixel count. LCD manufacturers were also the first to come up with 1080p screens and to a certain extent, this was also used to a great extent by LCD TV retailers as a sales advantage over plasma TVs.

This is no longer the case; for anything greater and including  42-inch screens, plasma TVs are readily available in 1080p full HD resolution. This means that the two display technologies are now on par in this respect.

Rather the situation with both plasma and LCDs is that you have more choice for 1080p HDTVs; additionally, 720p LCD TVs at anything bigger than 37-inch have become almost inexistent.

A word of caution: Do not underestimate the picture quality supported by the less expensive 720p display. Keep in mind that the eye would not be able to perceive the additional picture detail afforded by the 1080p pixel count for screens less than and including 50-inch diagonals from what is considered normal viewing distance especially with TV program content. Rather, opting for a 720p instead of a 1080p HDTV for anything between 40-inch and 50-inch would definitely lead to significant savings since the higher pixel count of 1080p plasma or LCD HDTVs comes at a price.

Up to very recent, LCD televisions used to deliver more in terms of pixels for screen sizes up to 50-inch. When comparing plasma vs LCD TV sets, it was only at the extreme larger end of the scale that plasma and LCD display resolutions met.

However, things changed. At screen sizes where collision between the two technologies occurs, plasma and LCD TVs are both available in 1080p resolutions. Rather, the real problem for the HDTV buyer is that 720p LCD TVs are no longer available within the 40-inch to 50-inch screen category.

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