LCD and Plasma Displays Buyer's Guide

New technology has revolutionized how and where businesses can use video. Both LCD and plasma displays are filling roles that traditional CRT screens never could - or didn't do well. In tradeshow booths, as lobby signs, in boardrooms, and mounted in retail stores, the modern flat-screen monitor takes up much less room and provides better picture quality than traditional television screens.

Plasma and LCD - what's the difference?
Plasma and LCD technologies both became widely available right around the same time, and both share a distinctive profile that's drastically thinner than traditional CRT monitors. This led to the two terms being used interchangeably when referring to flat screen monitors, when actually the two are very different types of screens.

In plasma screens, each individual pixel (the dots of light that make up the picture) is basically three miniature fluorescent lights: one blue, one green, and one red. Each is controlled individually to create the full spectrum of colors visible to the human eye.

In contrast, LCD screens use one backlight as the illumination source for the entire screen. Thin-film transistors (TFTs) control a matrix of liquid crystals, applying an exact voltage that makes the crystals "untwist" in specific ways and direct light from the back through to the screen. As in plasma displays, there's one cell for each of the three colors that make up a pixel. If all three colors open all the way, the pixel displays white - different voltages are used to combine light from the three cells into the desired color and intensity.

• Size. Plasma displays are generally larger than LCD displays. Plasma screen sizes generally range from 32" to 65", while most LCD screens are 13" to 45".
• Viewing angle. Because each pixel is lit individually, plasma televisions have viewing angles of 160°, meaning you can still see the entire picture from 80° to each side and up and down. Even the newest LCD displays only have viewing angles of about 130° to 140° -- and in addition, while you can see the entire picture from an angle, the picture quality gets worse rapidly.
• Color. Most viewers find that plasma displays offer better color saturation: deeper, more vibrant hues. However, LCD displays produce static images with crisper detail and even coloration.
• Burn-in. On plasma displays, static images begin to "burn in" to the screen in as little as 15 minutes. This means that if your display is going to be used to show the same images for long periods of time, the pixels will begin to deteriorate, reducing their effectiveness and color accuracy. LCD displays aren't susceptible to this problem.
• Contrast. As in photography, contrast is a measure of how dark black shades appear compared to whites on a given display. Plasma screens have contrast ratios of around 3,000:1, while most LCD displays only reach around 800:1. The contrast on an LCD screen is still quite good, but it's outstanding on plasma sets. Note that some of the latest LCD models are now reaching the 3,000:1 mark.
• Lifespan. The gases that produce plasma screen's brilliant colors leak out over time. After about 25,000 to 30,000 hours of use, the display will be about half as bright as it was new - and it will simply continue to get dimmer. That's around 3 to 3½ years of constant usage. LCD displays last about twice as long: average lifespans are around 60,000 hours.
• Tuners. To receive television signals, your monitor will need a tuner. Most LCD displays come with a tuner, while many plasma screens don't. If you want to be able to watch any broadcast TV on a plasma screen, make sure the model you choose includes a tuner.

What are you using it for?
Given these characteristics, there are some situations where it clearly makes sense to choose one type of display over the other. For 24x7 usage as a sign or noticeboard, LCD screens are by far a better choice, due to their longer lifespans and immunity to screen burn-in. They also use much less electricity than plasma displays. For high-impact video and larger audiences, large plasma screens produce better contrast and sharper colors over a wider range of viewing positions.

For mixed use, the choice isn't always as clear. Compare the performance of both types of screen on the applications you expect to use most: DVDs, PowerPoint presentations, or any other video source.

LCD and plasma displays pricing
The two most important factors in determining price are the physical size of the screen and its resolution. Resolution is measured in the number of pixels horizontally and vertically: small LCD displays can have resolutions as low as 480 x 640. If your display is going to run off of a computer, it's important to make sure that the display can handle the same resolution as the computer. Right now, 1024 x 768 is the most common computer resolution.

Pricing for both LCD and plasma televisions has fallen drastically in recent years, but due to the varying resolutions, prices vary quite a bit within each size range. In general, plasma TVs are less expensive than LCD screens of the same size and resolution. Here are some typical price ranges for both types of flat screen monitors:

A few manufacturers are producing even larger plasma screens - you can find 84" models, but prices are over $40,000.

When comparison-shopping, be aware of "B stock" deals. This broad category includes customer returns, floor models, trade show demos, missing accessories, and other "slightly used" models. Dealers inspect and repackage them, but they aren't always covered by manufacturers' warranties.

• HD or not HD? Contrary to some people's assumptions, an expensive HD (high-definition) monitor does not always produce a better image than another monitor with similar characteristics. If you're going to be using your monitor to watch HDTV or to display high-resolution computer images (1024 x 768 is a common example), the picture will be significantly better on an HD monitor. However, if you're going to be using standard video signals, an HD screen is often no better and in some cases actually performs worse than an ED (enhanced definition) screen.
• What about DLP? Digital light processing (DLP) technology packs up to 1.3 million microscopic, hinged mirrors onto a single computer chip. Light is reflected by these mirrors and through a rapidly-rotating color wheel to produce images on the screen. DLP works best at larger sizes - they range from 43" to 65". They produce contrast ratios as high as 5000:1, are not subject to burn-in problems, and are less expensive than similar sized plasma or LCD screens. They do require occasional bulb replacements - about every 8,000 hours or so - but replacement bulbs only cost about $250 - $350. As they become more widely available, expect to see more of them in all kinds of applications.
• Watch out at altitude. Because plasma displays use pressurized gases as part of producing images, they are quite sensitive to changes in atmospheric pressure. At altitudes over 6,500 feet, plasma displays produce a distracting buzzing noise that can really detract from their sleek look. (For this reason, you'll only see LCD screens in airplanes - even though they're pressurized, the pressure differentials are enough to cause this problem.)
• Know your inputs. Most plasma and LCD monitors accept all common video formats. These include composite, S-video, and component video input, along with RGB inputs to accept computer video. However, every display includes a different set of inputs, so take the time to verify that your set has all the inputs you'll need.
• Put it anywhere. One of the advantages of flat screen monitors is their versatility. You can get many types of mounts for your new display: flat wall mounts, tilting/extendable wall mounts, table stands, mobile carts, ceiling mounts, and more.

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