In the TV market, two technologies are currently competing for your hard-earned dollars (plasma and LCD), and another is on the way (OLED). Let's first examine the great "plasma vs. LCD" debate, then we'll discuss how OLED could change the landscape, when (if?) it arrives. In discussing plasma and LCD, both display types can produce a very attractive picture. Each technology has its own potential strengths and limitations that suit it for a certain type of environment or use; understanding these differences will make it easier to choose the display type that best suits your specific needs.

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Plasma
Plasma has long been the videophile's choice for TVs, and the primary reason is its innate ability to produce a truly deep black level. Black level is a fundamental building block of a TV's picture quality. The deeper the black level, the more rich and saturated the image can look. Plasma pixels generate their own light (the gases inside the cells, when ionized by an electrical current, emit UV rays that causes the phosphors to glow), while LCD pixels rely on an external light source. Theoretically, each plasma pixel should be capable of a perfect black; however, in order to react quickly to signal changes, plasma pixels are in a primed state that does emit some light. Improvements to the priming method result in continued improvements to plasma black levels. A TV with a deep black level can produce a more saturated, dimensional image in a dark or dim room, which makes plasma a good choice for those people who have a dedicated theater room or primarily watch TV at night in a medium to dark room. Furthermore, because each plasma pixel is self-illuminating, this technology can often do a better job reproducing fine black details and subtle shading within a scene. This can be important when watching films, which are often darker and more complexly lit than TV shows and sports content - another reason why plasma is a popular choice amongst film enthusiasts.

On the other end of the spectrum is light output, or brightness. Plasma TVs can produce very bright elements within a scene, which combined with the deep black level results in outstanding image contrast. However, the entire image is seldom as bright as what you can get from an LCD. When a reviewer measures the brightness of a plasma TV using a smaller white window surrounded by black on the screen, the brightness number can be quite high. However, the brightness of an all-white screen will be much lower. Since each plasma pixel generates its own light, it requires a lot more energy to illuminate every pixel for an all-white screen, which is also why plasma TVs aren't as energy-efficient as LCDs when watching brighter content. When an entire scene is bright (like a daytime sporting event), a plasma image seldom looks as bright as an LCD. Another potential limitation to plasma is the fact that the screen is made of reflective glass, which allows you to see room reflections in a brighter environment. The anti-reflective filters used in newer plasmas help to lessen this concern, but the lower light output and screen reflectivity still make plasma a less-than-ideal choice for a really bright, sunlight viewing area.

Arguably the biggest concern for shoppers when it comes to plasma is the issue of image retention or "burn in." When static images -- like the sidebars in 4:3-shaped TV shows, sports tickers, or news/stock crawls -- are left on the screen for a long time, the plasma pixels wear unevenly, leaving visible outlines on the screen. Permanent burn-in was an issue with early plasma models, but it's not really a concern anymore; however, some plasma TVs still exhibit short-term image retention - you may see some outlines, but they fade over time. In today's market, just about every plasma offers features in the setup menu designed to prevent or counteract the effects of image retention. The Pixel Orbiter function will subtly shift the image to prevent one group of pixels from holding the same image too long, while the scrolling bar helps to more quickly "erase" any short-term retention that might occur.

One final plus for plasma is that the technology offers a very wide viewing angle; the image brightness and black level remain consistent when you view it from extreme side angles or place the TV higher on the wall. That is not the case with LCD (see below).

LCD
Unlike the self-illuminating nature of plasma pixels, LCD pixels require an external light source. In years past, that light source was generally a cold cathode fluorescent (CCFL) light placed behind the screen, but these days a growing majority of LCD TVs use LEDs (light emitting diodes), placed either behind the screen or around the screen's edges. LEDs are more energy-efficient than CCFLs and don't contain mercury. An LCD TV's greatest strength is its light output: These TVs can generally produce a very bright image, which makes them a good fit for someone who does a lot of daytime viewing in a well-lit room. Brighter content - HDTV shows, games, and sports -- can really pop on an LCD TV.

On the other hand, because the technology uses an always-on light source, LCD struggles to produce a truly deep black level. Blacks can often look grey, fine shading is often absent, and the picture can look washed out in a dark or dim room. Most current LCDs include an adjustable backlight that allows you to make the TV brighter (for better daytime performance) or darker (for better nighttime performance), but even at its dimmest setting the TV's black level is still not as good as you can often get with plasma. Also, many of today's LED-based LCDs only put the LEDs around the edges of the screen and then direct the light inward. This design allows for a very thin, lightweight form, but it's more challenging to illuminate the entire screen evenly. In dark scenes, you may notice that the corners or outer edges of the image look lighter than the center of the screen; we call this a lack of screen uniformity, but some people often refer to it as "clouding."

To address the issue of the always-on backlight, LCD manufacturers introduced the concept of local dimming in LED-based LCDs. Local dimming allows the TV to independently adjust the brightness of the different zones of LED lights: the light can remain bright in bright areas of the scene and be dimmed or turned off completely in dark areas. This has enabled LCD TVs to better compete with plasmas in terms of black level and overall contrast; the better performers can produce incr
edibly deep blacks while still allowing bright areas to remain bright, resulting in great image contrast. The drawback to local dimming is that, depending on how many LED zones the TV has, the effect can be imprecise, causing you to see glowing or halos around bright objects. Also, local dimming is usually only offered on the highest priced LED-based LCDs, so you have to pay a premium to get the premium performance.

LCD TVs of yore also struggled with the problem of motion blur. The combination of the slower response time of the liquid crystals and the always-on backlight created blur that was especially visible with faster-moving action and sports content. LCD pixel response times have consistently improved over the years, and manufacturers now offer LCD TVs with higher refresh rates of 120Hz and beyond to further cut down on motion blur. The addition of more frames, compared with the traditional 60Hz TV, helps reduce the visibility of motion blur and can (depending on how those extra frames are created) also reduce film judder. Again, though, the lower-priced LCD TVs in a company's line may still only be 60Hz, so motion blur may be noticeable (some people are more sensitive to motion blur than others).

As I mentioned above, LED-based LCDs are very energy-efficient even at larger screen sizes, and they can have a very thin, very light form factor, which makes them perfect for wall-mounting. Some LCD screens (usually the lower-priced models) have a matte finish that does not reflect light, so you don't have to worry about seeing room reflections from windows and other light sources on the screen. If you're looking for a TV to be placed in a very bright, sunlit room, you might want to shop for a model with a matte screen. However, a growing number of LCD TVs now use reflective screens designed to reject ambient light to make black levels look darker in a bright room. These screens can sometimes be even more reflective than plasma glass.

Short-term image retention is not a concern for LCD, as it is with plasma. On the other hand, LCD viewing angles are not as good as plasma's. LCD image saturation drops off as you move to the sides, sometimes significantly so. That means the picture won't look as good for people viewing the screen from a wider angle; bright images might still look okay, but darker images will become even more washed out. If you have a large room with seats in a variety of locations, LCD may not be the best choice.

OLED
OLED stands for Organic Light Emitting Diode, and the technology could combine the best of both plasma and LCD. Like plasma, OLED pixels generate their own light. An OLED consists of a thin film of organic carbon-based compounds sandwiched between two electrodes. When the compound receives an electric current, it emits light. An OLED TV can produce a true black (no electric current equals no light, and it does not need to be primed the way plasma does), yet it can also be extremely bright, like an LCD. The result is an image with outstanding contrast. Motion blur and viewing angle should not be concerns, either. With OLED, all of the compounds and circuitry can reside within one very thin, light (even flexible) sheet, so the TVs can have an even thinner, lighter form factor than edge-lit LED/LCDs.

The biggest drawback to OLED is that, as we write this in March 2013, the TVs still aren't available on U.S. store shelves. Back in 2008, Sony ushered in the OLED era with the launch of the XEL-1, an 11-inch monitor that cost $2,500, earned rave reviews, and is no longer being produced. Since then, manufacturers have promised larger-screen OLED TVs, but none have materialized. Samsung, LG, Sony, and Panasonic all showed off 55-inch-or-larger OLED TVs at the recent CES 2013, with LG promising a March release date in the U.S. So far, it hasn't happened. The problem is that larger-screen OLED TVs are proving difficult to produce reliably; according to reports, only 10 percent of the TVs that come off the production line are functional. So, scheduled release dates continue to come and go as manufacturers continue to try and increase yield numbers.

Truth be told, until reviewers can get their hands on real-world samples, we won't know if OLED technology will truly live up to its performance potential. What we do know is that the first crop of OLED TVs will be very expensive (LG's 55EM9600 is listed at $11,999). If OLED performance does prove to be as good as we hope, then these TVs will clearly be targeted at the higher-end videophile, not the everyday consumer - at least at first. This will be a luxury item for the enthusiast who wants the pinnacle of performance and is willing to pay a premium to be an early adopter.

Additional Resources
• Read more original content like this in our Feature News Stories section.
• See related stories in our Plasma HDTV and LCD HDTV news sections.
• Explore reviews in our HDTV Review section.