Since their introduction in 1993, plasma monitors have engendered a reputation for effective public signage and business display with a hint of sexiness thanks to their vibrant images and thin physical form. As little as a year ago, plasma monitors seemed a sure bet to dominate the self-contained panel display market. Yet, there’s another display technology — the familiar liquid crystal display (LCD) — that has emerged as an alternative to plasma and shares many of its advantages, including the efficient use of space and sleek sex appeal.
LCD technology has been used for years in notebook computers and more recently as space-saving desktop replacements for big-belly CRT computer monitors. The difference now is that LCD manufacturers are finding ways to make their monitors much larger, thus comparable to plasma in many of the same target markets.

The fundamental difference between plasma and LCD displays is the way each technology produces images and brightness. Some of these differences — for instance power consumption, resolution, and contrast — give one display type a distinct advantage over the other in specific applications. There are also very overt differences in physical size and price, where plasma’s relative maturity in the large-panel display market holds a clear edge. That’s likely to change over the coming months as LCD makers implement ongoing R&D efforts to close those gaps.

What’s already clear is that these thin and flat panels have changed the figurative and literal face of public display and signage, business presentations, and to some extent home entertainment. Plasmas are now regular fixtures in airport lobbies showing flight arrival and departure information, in shopping malls strutting new products and special offers, and in many smaller conference rooms where front projection is less practical.

In this Resource Guide, we focus on plasma and LCD flat panels of 20 diagonal- inches and larger. That ignores the extensive market for flat-panel, desktop computer monitors, where LCDs dominate and plasmas don’t even compete. It also ignores a quickly growing market for LCD-based consumer television sets that, while perhaps not directly affecting the professional AV market, confirms the technology’s march forward into new video-centric arenas. However, the following analysis of each technology and the accompanying list of LCD and plasma display products, which begins on page 6, clearly underline the comparable and competitive aspects of the two monitor types in the large display market for pro AV applications.

Technical Advantages and Iimitations
Both plasma and LCD displays use fixed-matrix technologies, but they pro-duce images in very different ways. Like LCD projectors, LCD monitors use a light source that’s behind and shining through a thin film transistor (TFT) layer and color filters that produce specific brightness and colors. The difference is that a projector uses a very small and focused light source while a large flat-panel monitor must use a light source that’s physically as large as the image it produces.

One of the main challenges to building larger LCD panels is creating the huge backlight panels required to adequately and evenly diffuse light, thus eliminating bright spots across the image. LCDs use an electric charge applied to the TFT to turn, or twist, the liquid crystals, thus allowing light to pass through. The more the liquid crystals twist out of the light path, the more light that reaches the color filters, the glass, and ultimately the viewer’s eyes.

Plasmas also use an electric charge, but that charge is applied directly to a mixture of neon-based gases (not unlike a tiny fluorescent light) in each sub-pixel of a plasma matrix. When stimulated, the gases produce light. Actually, they produce ultraviolet light that in turn excites red, green, and blue phosphors to emit light and create different colors. When looking at a plasma monitor, the viewer is looking directly at the light source.

What do those technical differences mean in terms of real-world images? Of course, there’s no substitute for seeing the panels in a side-by-side comparison, but here are several less objective areas where plasmas and LCDs differ. Depending on your specific application, one or more of these traits may make your technology decision an easy one.

Size
Naturally, size matters and right now it’s easier for plasma manufacturers to build larger panels. Today’s largest plasmas top 60 diagonal-inches, limited primarily by the price of producing larger pieces of glass. Smaller, "value-oriented" plasma models are generally 32 to 40 inches.

By comparison, relatively diminutive LCD panels today top out just above 40 inches, and anything greater than 24 inches is considered large. That’s almost sure to change over the coming months as LCD makers scramble to get in the game with new, larger form factors. You can expect announcements over the next year that close the size gap against plasmas.

Resolution
While plasmas are physically bigger, LCDs arguably can do more through higher native resolutions. Higher resolution translates to sharper images, more legible text, and less posterization. Native resolution can be particularly important because both of these fixed-matrix technologies produce much clearer images when configured at that native resolution rather than scaled to a different resolution.

Brightness & Contrast
All things equal, plasma monitors have a brightness and contrast advantage over LCD monitors. Since LCD panels use a backlight passing through multiple layers, some amount of light is necessarily blocked from reaching the viewer’s eyes. The light source is also physically farther away compared to a plasma monitor, where the viewer is literally looking right through the glass at the source of light. LCD makers can compensate with brighter backlights, provided that the light can be evenly diffused.

Arguably, a more important difference, depending on specific use, is the fact that plasmas are more affected by ambient light than LCDs because they tend to reflect more outside light, brightening blacks and dark colors and lowering effective contrast.

Color
Just as LCD computer monitors have generally come up short against CRTs for rich, accurate colors, LCD’s color filter blending can fall a little short of the more direct phosphor blending of plasmas. That said, many graphics pro-fessionals now consider LCD computer monitors suitable for professional work, and LCD flat panels use much the same technology. And it could be argued that uncontrolled ambient light will affect a viewer’s perception of color more.

Power Consumption
Plasma monitors use roughly 50 percent more power than similarly sized LCD panels under the same conditions. When comparing 40-inch panels, the plasma will cost an additional $100 per year on an electric bill — a significant expense when dozens or hundreds of displays are employed, such as in an airport or casino betting parlor. On a per-panel basis, however, $100 per year is clearly a very minor part of the overall cost.

Burn-in
Aside from physical destruction (breaking the glass), there is no greater long-term danger to plasma monitors than burn-in. Indeed, burn-in is itself physical damage that permanently affects the displayed image when overused phosphors ultimately change their physical properties. Burn-in is most easily visible as ghosted images, though it also leads to poorer contrast and less accurate colors. The most recognizable burn-in problems occur when text characters have been displayed for long periods of time, although burn-in does inevitably happen with all plasmas and all phosphors over time.

The best hope for plasma longevity is "burning" a monitor evenly over the entire image surface. To do so, some manufacturers have incorporated pixel shifting and negative display modes that help balance the wear across the screen. Of course, that literally means burning-in little-used areas to match the burn of frequently used pixels.

LCD can suffer from a similar type of image retention or ghosting, but the effect is not permanent.

Viewing Angle
LCD technology has a well-earned reputation for poor off-axis viewing. Notebook computer monitors are a perfect example of this: If you’re not looking straight at them, the image is difficult to see. However, there has been an ongoing push by LCD manufacturers to increase viewing angle, and today’s AV panels generally do just about as well as plasma. You’ll regularly see specs for each technology boasting a 160-to 170-degree viewing angle.

Longevity
Because of burn-in, and to a lesser extent power consumption, LCD monitors are likely to last at least two and maybe three times longer than similarly used plasmas. What’s more, the most likely component of an LCD to wear out is the back-light panel, which is often replaceable. On the other hand, with proper use and diligent burn-in prevention, plasmas may last past a normal depreciation or technological lifespan.

Price
Plasma monitors have been available longer than large-form LCDs and many plasma companies are now in their third and fourth product generations. That simple advantage helps give plasma a significant price advantage over LCD, often half the cost for a similar size.

Understanding the differences between Plasma and LCD displays.

What's the difference between a plasma display and an LCD flat screen, and how do these differences enter into your decision-making process? Often "plasma" is used as a general term for thin, flat displays or monitors, but there are some general differences in the technologies, as listed below. Overall, LCD is great for displays 28-inches and smaller, and plasma is ideal where 32-inches or larger display is needed. They are complementary technologies. Please note, we just are starting to see LCD's that are designed for video/TV use where several of the items below may be subject to qualification.