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Flat-screen plasma and LCD TV buying guide

Get a bargain on the smoothest, sexiest HD TV

If you're not planning to hang your TV on the wall, is a flat-panel the best way to go? And which are better: plasma or LCD flat-screen TVs? Here's what you need to know before you buy.

The specifications explained

Gone are the days when you figured out how big a screen you wanted, looked at some sets, and bought the one with the best picture that fit your budget. An options explosion has littered the shopping landscape with numbers, features, and terminology that even experts sometimes have trouble tracking. So we've tried to boil the choices down to the basics that can actually do you some good, and we've noted which are important. (In audio and video, never forget that just because something has a number to describe it doesn't mean it really matters!)

We've grouped the specs into three categories: important, somewhat important, and minor.

Important: contrast ratio

Contrast ratio refers to the brightest and darkest light values a display can produce at the same time. All else being equal, the higher the contrast ratio is, the better. All else is seldom equal, however.

Pumping up the maximum light output, for example, can increase contrast, but it won't do anything to overcome poor black level, which tends to be a greater problem with plasmas and, especially, LCDs. So take contrast ratings as a very rough guide to be supplemented by eyes-on evaluation.

That said, LCD contrast-ratio specs start at about 600:1, while those for plasmas start at about 1,000:1 or better. Although ratings of 10,000:1 or better are becoming common for both types of displays, you should approach them with skepticism; whether any of them accurately reflect performance under real-world conditions is doubtful.

Important: aspect ratio

The aspect ratio describes the relationship of screen width to screen height. Conventional sets have a 4:3 aspect ratio, whereas widescreen models are 16:9. Wide screens are the future. HDTV is a widescreen format, for one thing. For another, DVDs usually look better on widescreen displays because nearly every movie made in the last 50 years was filmed in an aspect ratio of either 1.85:1 (very close to 16:9, which is 1.78:1) or 2.35:1 (even wider than 16:9).

Somewhat important: resolution

Non-CRT displays, such as plasmas and LCDs, are fixed-pixel arrays, which means they have rows and columns of individual picture elements that turn on and off to produce the necessary patterns of light.

Resolution is specified as the number of pixel columns by the number of pixel rows - 640 by 480, for example, or 1280 by 720. Resolution and, to a somewhat lesser degree, contrast ratio determine perceived picture detail.

Digital content currently is delivered in one of five formats: 480i, 480p, 720p, 1080i, and 1080p. The 480i format is the same as that used for standard analogue TV, and when programming originally in 480i is delivered by digital cable or satellite to your home, it retains that format. DVDs are sometimes mastered in 480p, but mostly they are 480i; a progressive-scan DVD player can deinterlace 480i DVDs to create 480p output, however.

The 720p and 1080i formats are used by satellite, cable, and over-the-air-broadcast high-definition content providers, as well as some advanced DVD players that upconvert 480i and 480p content. Blu-ray and HD-DVD discs carry 1080p video, although their corresponding players can deliver the content in 1080i or 720p format for displays that do not accept 1080p input.

Generally speaking, a display is considered high-definition if it is widescreen and has a total pixel count approaching 1 million. So 1920 by 1080, 1280 by 720, 1366 by 768, and 1024 by 1024 are all examples of high-definition display resolutions. Small differences are not very consequential at greater than 1280 by 720, the specified resolution of the 720p high-definition format.

Any resolution of 1280 by 720 or greater is best for viewing high-definition broadcast and DVD content; if you sit close to a large screen (50in or greater), you may prefer a 1920 by 1080 (1080p) display, but the increased picture detail afforded by such a high-resolution display will be difficult or impossible to see on a smaller screen unless you are sitting very close to it (less than 3m). Non-HD widescreen is called enhanced-definition; a typical ED resolution is 852 by 480. Standard-definition, or SD, includes 640 by 480 and 720 by 480. Enhanced-definition displays are better than standard-definition for 480p content such as that from progressive-scan DVD players.

Important: video inputs

The number and type of video inputs determine which sources you can use with the display.

Composite video: this input type has the lowest quality but the broadest compatibility. Any device that has video outputs will include composite video among them. Connection is made with a single 75-ohm coaxial cable between RCA jacks.

S-Video: S-Video offers better quality than composite video, and most video sources except standard VCRs now have S-Video outputs. Connection is made with a special cable and multipin sockets.

Component video: this high-quality option is the minimum standard for connecting high-definition cable and satellite set-top boxes and progressive-scan DVD, HD DVD and Blu-ray Disc players. It requires three 75-ohm coaxial cables of the same type used for composite video.

VGA: video graphics array is a high-quality analogue RGB connection used primarily for computer connections.

DVI: this is one of the highest-quality types of inputs. Digital visual interface is a digital video connection that can attach to devices with HDMI outputs (see below) by means of an adaptor. It may also be used for computer connections. Requires a special cable and multipin sockets. Some displays with a DVI input may work only with computers, so watch out for that if you plan to connect an HDTV source, such as an HD digital cable box or an HD DVD or Blu-ray Disc player. Another thing you need for guaranteed HDTV compatibility is compliance with the HDCP (High-bandwidth Digital Content Protection) system.

HDMI: also of the highest quality, High-Definition Multimedia Interface is basically DVI plus a digital audio and control link, and it normally incorporates HDCP; it can be mated to DVI with adapter cables. This connection is provided on almost all current HD satellite receivers, HD cable boxes, and upconverting DVD players (those that provide 720p, 1080i, or 1080p output from regular DVDs), and it is the standard video connector for Blu-ray and HD DVD players. The exact version of the HDMI input (for example, 1.1 or 1.3) is of little consequence on TV sets. If you have, or plan on getting, an HD DVD or Blu-ray Disc player, it is desirable, though by no means essential, that the TV's HDMI inputs be capable of accepting 1080p signals.

Somewhat important: built-in tuners

Most current flat-panel displays include a tuner for conventional analogue broadcast and cable TV reception and for broadcast HDTV. A few, however, are strictly displays, or monitors, with no built-in tuner (a more common setup for plasmas than for LCDs).

That may not matter if you receive all your TV programming via satellite or cable, but if you want to watch broadcast TV over an antenna, be sure that the set you buy includes a TV tuner. Many sets also have built-in tuners for digital cable TV. Although such tuners have a standard for handling scrambled premium channels (for example, HBO), many sets do not support it, so be sure you know exactly what you are getting.

If you want that capability, make sure the set you buy has a CableCard slot and that your cable provider can provide you with the necessary electronic ID card. Cable pay-per-view and satellite TV currently require external set-top boxes.

Minor: comb filter type

Comb filters are necessary in analogue TV to separate colour and luminance information without losing too much detail, but that's not an issue in HDTV. The only time the comb filter comes into play is for analogue TV reception or any signal coming in via a composite video connection. For all other connections, it's out of the loop. In any case, the comb filters in flat-panel TV sets are routinely very good these days.

LINKS:

The big picture

LCD and plasma screens may look similar, but the underlying technologies are quite different, as are, consequently, their strengths and weaknesses. Click here for the big picture: our guide to the underlying technologies behind flat-screen TV.

The specifications explained

Perplexed by pixels? We explain the significance of the most meaningful specifications. Here's our simple explanation of what HDTV specifications mean, and which you should care about.

Flat-screen TV shopping tips

Read our advice to pick the panel that's right for you. Look no further for expert flat-screen TV buying advice.


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