Plasma vs. LCD: Which Is Right for You?
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By Adrienne Maxwell
In the flat-panel HDTV marketplace, two main technologies are competing for your hard-earned dollars: plasma and LCD (or liquid crystal display). While each camp has its diehard loyalists, the truth is that both display types can produce a very attractive picture. Each technology has its own potential strengths and weaknesses that suit it for a certain type of environment or use; understanding these differences will better enable you to choose the display type that best accommodates your specific viewing needs.
A key difference between LCD and plasma involves the manner in which each technology generates the light needed to produce an image. Plasma pixels generate their own light, while LCD pixels rely on some form of external light, traditionally a fluorescent backlight. This backlight can usually be very bright, so LCDs are generally capable of much higher light output than plasmas. Most LCDs also use non-reflective screens. These two traits make LCD a good fit for a really bright viewing environment. However, because the backlight is always on, a traditional LCD has difficulty rendering a truly deep black level. Blacks often look gray, fine shading can be absent, and the picture may look washed out in a completely dark room.
In contrast, because plasma TVs don't use a backlight, they are generally able to produce deeper blacks and offer finer shading than a traditional LCD, which makes them a better choice as a theater display or if you plan to watch a lot of content at night in a dark room. 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. Plasmas that employ less priming have better black levels than those that employ more. Plasma TVs are seldom as bright as LCDs, and their screens are made of glass, which is reflective. The use of an anti-reflective filter helps cut down on screen reflections, but plasma still isn't recommended for a really bright, sunlit viewing area.
Plasma TVs have a wide viewing angle; the picture quality remains consistent when you view it from the side or place it higher on the wall. While many LCDs can still produce a watchable image at wider angles, the picture loses a lot of saturation and detail, so you should be mindful of where your seating area is in relation to the TV. Viewing angle can varying greatly between LCD models, so it's important when shopping to check out each TV's performance from wider angles.
An LCD's ever-constant backlight can create other problems - most notably, motion blur that's especially visible with faster-moving action and sports content. Motion blur occurs because the constant backlight does not give your eyes the break they need between frames; your eyes blend the frames and cause you to perceive image blurring. Some people are more sensitive to this effect than others. Again, because plasma doesn't use a constant light source, motion blur is not a problem.
Advancements in LCD technology have addressed some of the issues created by the backlight. A 120-hertz LCD doubles the TV's frame rate (a standard TV has a 60Hz frame rate) to help reduce motion blur, and it is often quite successful at doing so. A new crop of high-end LCDs use lots of individual LED backlights instead of fluorescent backlights; "local dimming" LED technology allows unneeded LEDs to remain turned off, so black parts of the image can look truly black. These TVs will also cycle through the LEDs that are illuminated to provide the needed break to reduce motion blur. Of course, these new features add to the TV's cost compared with a traditional LCD.
Arguably, the biggest concern for shoppers when it comes to plasma is the issue of image retention, or "burn in." When static images like 4:3 sidebars, gaming score panels, or news 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 is not really a concern anymore; however, some plasmas still exhibit short-term image retention - you may see some outlines, but they fade. Still, if you plan to watch a lot of SDTV content and prefer 4:3 sidebars to incorrectly stretched aspect ratios, you may want to consider an LCD, or at least look for a plasma model that offers features (gray sidebars, white wash patterns and orbiters) designed to help prevent or counteract the effects of image retention.
As both plasma and LCD technology continue to evolve, the performance differences grow less obvious. Especially as you move into the higher-end realm, your choice becomes less about plasma vs. LCD and more about one model or brand vs. another. Still, the general guidelines presented here give you some performance issues to keep in mind when you head to the store.
Keywords
Plasma, LCD, liquid crystal display, backlight, fluorescent backlight, non-reflective screens, anti-reflective filter, viewing angle, motion blur, 120Hz, LED, local dimming, image retention, burn in
