The Specs 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 (not us, though). We've cut through the chaos to give you the information you need to get up to speed. When you're finding your way in the high-def, A/V world, don't just go for the gaudiest numbers--sure, some are important, but others aren't. Let's quickly walk through a few.
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, will increase contrast, but it won't do anything to help pitiful black levels--that, in our opinion, is a much greater concern. LCDs in particular have a tougher time dealing with darks. So take contrast ratings as a very rough guide to be supplemented by eyes-on evaluation. LCD contrast-ratio specs start at about 600:1, while those for plasmas start at about 1000:1. Although ratings of 10,000:1 or better are becoming common for both types of displays, you should approach such claims with a healthy bit of skepticism. Trust your own eyes. Keep in mind that when you're on a showroom floor, you're checking out the HDTVs under the store's lighting conditions, not yours. Will you watch in a dark cave or in a well-lit, open space? Probably the smartest idea is to check the store's return policy before buying.
Important: Aspect Ratio
The aspect ratio describes the relationship of screen width to screen height. Conventional sets have a 4:3 aspect ratio, whereas wide-screen models are 16:9. Wide screens are the future. HDTV is a wide-screen format, for one thing. For another, DVDs usually look better on wide-screen 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).
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 does, 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, Blu-ray Disc, and HD DVD players. It requires three 75-ohm coaxial cables of the same type used for composite video.
VGA (Video Graphics Array): This high-quality analog RGB connection is used primarily for computer connections.
DVI (Digital Video Interface): One of the highest-quality types of inputs. This digital video connection can attach to devices with HDMI outputs (see below) by means of an adapter. 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 a Blu-ray Disc or HD DVD player. Another thing you need for guaranteed HDTV compatibility is compliance with the HDCP (High-bandwidth Digital Content Protection) system.
HDMI (High-Definition Multimedia Interface): Also of the highest quality, this is basically DVI plus a digital audio and control link. The big draw here is that you get a one-wire setup that pumps HD content into your other home-theater components too. 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 currently on the market. If you have, or plan on getting, a Blu-ray Disc or HD DVD player, it is desirable, though by no means essential, that the TV's HDMI inputs be capable of accepting 1080p signals (we'll get to 1080p in a second). Don't have HDMI components? Don't sweat it: Simple adapters turn HDMI into DVI connectors. Finally, for what it's worth, movie and TV studios love HDMI because it incorporates HDCP to combat piracy.
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 analog 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, though 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 wide-screen and has a total pixel count approaching 1 million. So 1920 by 1080 (1080p), 1280 by 720 (720p), 1366 by 768, and 1024 by 1024 are all examples of high-definition display resolutions.
Somewhat Important: Screen Size
Size matters, don't get us wrong. But just because you can afford a 65-inch monster doesn't mean you should buy one. You need to factor in the screen size and where you plan to watch the TV. Having your nose pressed up against the display in a broom closet of a room is hardly "ideal viewing conditions."
To determine the best viewing distance, and therefore how much space you'll need in your TV room, remember this simple bit of math: Note the screen size in inches and multiply it by 2. Calculators ready? Take, for example, a 52-inch set. The sweet spot for viewing is 104 inches away, or a little more than 8.5 feet from the screen (8.66666667 feet if you want to be nitpicky about it). You don't have to be exactly on target. Just bear this in mind as you plan where to place your new set.
Somewhat Important: Built-In Tuners
Most current flat-panel displays include a tuner for conventional analog broadcast and cable-TV reception and for broadcast HDTV. A few, however, are strictly business--they're monitors with no built-in tuner (more common 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 give you 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 analog TV to separate color 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 analog 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.
