What You Need to Know Before Buying an HDTV

Published February 28, 2007

| PCMag

The only thing worse than being unable to attend a favorite sporting event in person is knowing that the event is being broadcast in high definition and that your current TV won't do it justice.

Classic sporting events such as the Super Bowl and the Daytona 500 drive many a pixel-deficient fan into stores in search of an HD upgrade, and more often than not, that quest ends with a thin, flat television.

Mounted on a stand or wall, flat-panel HDTVs are tempting the eyes of sports fans with detailed imagery at increasingly affordable prices.

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Manufacturers now measure flat-panel longevity in decades, not years, so you'll have to live with your decision.

Ensuring long-term satisfaction with an HDTV is easily accomplished with a little planning and some basic knowledge about what makes each of these HD display technologies tick.

It's One or the Other

All flat-panel TVs are based on one of two competing display technologies: liquid crystal and plasma.

Although the manufacturers in each camp are quick to point out the supposed weaknesses of the other's technology, steady advances on both sides have resulted in near-parity of image quality, features and price.

This parity provides the prospective flat-panel buyer with a great selection to choose from. The big decision between buying a liquid crystal display (LCD) and a plasma display panel (PDP) becomes a personal choice based on one's budget and sense of style.

Even so, each of these flat-panel technologies has its own strengths and weaknesses, so a realistic assessment of where and how a new flat-panel TV will be used is an important first step toward narrowing the field of high-def candidates.

Plasma Comes of Age

The first plasma televisions went on sale back in 1997. The premium pricing of those early models, as well as their susceptibility to permanent image retention (also known — and dreaded — as "phosphor burn-in"), made them a tricky investment.

Today's plasma TVs are an immeasurably hardier lot; new phosphor formulas and display techniques significantly reduce the chances of an all-night session of ­"Guitar Hero 2" causing permanent damage.

These new phosphors also produce brighter and more accurate colors while extending the display's longevity (or so the manufacturers state).

Like traditional CRT displays, plasma display panels are an emissive display technology, meaning that the light that reaches your eyes is generated on the surface of the display. The main benefit of this display type is that the ­resulting picture appears the same from any angle.

Today's plasmas are touted as lasting up to 60,000 hours — that's about 8 hours of daily operation for over 20 years.

LCD manufacturers make similar claims. Chances are — even if the promises are no more than half true — that you will be staring at the flat-panel TV purchased today for a long time to come.

What's In an LCD?

LCDs are a transmissive display technology, meaning that the light that makes up the image on the screen is generated by fluorescent lamps behind the screen's surface.

Light from these very bright lamps passes through a "sandwich" of diffusion and polarization layers before reaching the liquid crystal matrix that we actually see. This matrix controls various pixel characteristics such as brightness and color.

The way an LCD manipulates light into the imagery we see has some inherent drawbacks that manufacturers are constantly working to improve.

Latency, a ghosting trail seen behind fast-moving objects, was an annoying characteristic that plagued the first LCDs. Improvements in video signal processing, as well as the ­increased switching speed of the pixels themselves, have effectively laid this image artifact to rest.

However, an LCD's ability to maintain crisp image detail when displaying scenes containing fast motion is dependent on a speedy refresh rate, or how many times the entire picture is updated every second.

The sandwich of components that guide an LCD's light to your eyes can also limit viewing angles. Though I've never seen a modern LCD exhibit complete picture loss at an extreme angle, it is common to note a loss of color saturation at angles as small as 20 degrees off center.

This loss of saturation is most noticeable in skin tones, as it gives people a pale or wraithlike appearance.

Display artifacts such as loss of color saturation are a good reminder to always judge a TV's image quality using content that features real people. The human face is inherently familiar to us, and we are quick to spot any oddities, genetics aside.

Also keep in mind that even the worst-performing TVs can look halfway decent when displaying animated movies. A display that does a good job of rendering natural-looking colors will have no trouble with highly saturated animation.

You Say You Want a Resolution

Experts agree that the four most important qualities of a "good TV picture" are image contrast, color saturation, color accuracy and resolution — in that order.

Modern liquid-crystal and plasma televisions are capable of excellent image contrast, and both camps continue to incorporate improvements in color accuracy and saturation.

Resolution may be last on the list, but spend some time in your favorite electronics store or shopping online and it becomes difficult to ignore the push toward 1080p.

That's shorthand for 1,920 by 1,080 pixels, progressively scanned — the highest resolution listed among the various video formats specified in the ATSC digital television standard, and the default resolution of HD DVD and Blu-ray Disc movies.

LCDs were the first flat-panels to offer true 1080p resolution, and now an increasing number of plasma TVs are making the shift toward 1080p.

LCD TVs that offer 1080p resolution start at 37 inches, whereas the smallest 1080p plasmas start at 50 inches (Hitachi plans to release a 42-inch 1080p plasma later this year).

A 1080p display offers about twice as many pixels as a 720p HDTV, and that ­extra resolution provides a number of benefits.

If you like to sit close to the screen, the additional pixels of a 1080p display will help deliver a more seamless and detailed image at larger screen sizes. A 1080p display is also an ideal match for the 1080i (interlaced) video format commonly used in broadcast HDTV.

Conversely, if you usually sit far away from the screen, or if the display is relatively small, the benefits of a 1080p display over a 768p/720p display are negligible.

This is one reason why the popular 32-inch and smaller LCD HDTVs have stuck with the native resolution of 1,366 by 768 pixels (768p), and most 42-inch plasma HDTVs offer 1,024- by 768-pixel resolution.

Don't Forget to Buy Cables

Getting the best image quality out of an HDTV also depends on the connection between the video source and the display. Nowadays, the best-looking video travels across one of two cable types: component video and HDMI.

Component-video cable is a common three-wire system that provides excellent image quality with standard and high-definition signals. Game consoles such as the Microsoft Xbox 360, as well as many cable and satellite set-top boxes, offer component-video output as the primary connection option.

HDMI (high-definition multimedia interface) has become the digital connection of choice on modern HDTVs, and it conveniently allows the transport of audio and video signals via a single cable. HDMI is also backward-compatible with the DVI connection commonly found on PCs.

As more and more video sources incorporate HDMI output, it becomes increasingly important to look for an HDTV that provides plenty of these critical inputs. A modern HDTV with two HDMI inputs is acceptable, but those offering three or more are becoming the norm.

There is some understandable confusion regarding the various versions of the HDMI spec, but the important thing to remember is that all HDMI cables are the same and that the latest iterations of the spec remain backward-compatible with older versions.

Focus more on the number of HDMI inputs you will eventually need, rather than on what specific features the connection supports.

Copyright © 2006 Ziff Davis Media Inc. All Rights Reserved. Reproduction in whole or in part in any form or medium without express written permission of Ziff Davis Media Inc. is prohibited.

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