How to Buy a Flat-Screen TV

The Specs Explained

• Introduction
• The Big Picture
• The Specs Explained
• Flat-Screen TV Shopping Tips

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. (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 better. However, all else is seldom equal. 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 rough guide to be supplemented by eyes-on evaluation. That said, LCDs tend to have contrast-ratio specs ranging from about 400:1 to 800:1. Plasmas start at about 600:1, with the really good ones clocking in at 1500:1 or better.

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 screen is 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: 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.

Generally speaking, a display is considered high definition if it is wide screen and has a total pixel count approaching 1 million. So 1280 by 720, 1366 by 768, and 1024 by 1024 are all examples of high-definition display resolutions. (Small differences are not very consequential; you would probably not see much, if any, difference between the three examples just cited.) Non-HD wide screen is called enhanced-definition; a typical ED resolution would be 852 by 480. Standard-definition, or SD, would include 640 by 480 and 720 by 480.

Important: Video Inputs

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

Composite video: Lowest quality but 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: Better quality, and most video sources except standard VCRs now have S-Video outputs. Connection is made with a special cable and multipin sockets.

Component video: High quality. This is the minimum standard for connecting HDTV tuners and progressive-scan DVD players. Requires three 75-ohm coaxial cables of the same type used for composite video.

RGB+H/V: High quality. An analog red-green-blue horizontal/vertical connection is sometimes used instead of component video. This input requires five 75-ohm coaxial cables of the same type used for composite video.

VGA: High quality. Video graphics array is an analog RGB connection used for computer connections and sometimes in place of RGB+H/V.

DVI: Highest quality. Digital visual interface is a digital RGB connection, commonly used for HDTV tuners and occasionally for DVD players; 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 tuner. Another thing you need for guaranteed HDTV compatibility is compliance with the HDCP (High-bandwidth Digital Content Protection) system.

HDMI: Highest quality. High-Definition Multimedia Interface is basically DVI plus a digital audio link and HDCP; it can be mated to DVI using adapter cables. This connection is used on some HDTV tuners.

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. Plus, the comb filters in flat-panel TVs are routinely very good.