Page 3 of 5   <       >

How to Buy a Flat-Screen HDTV

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 the quality is. 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. Since no true standard method for measuring contrast ratio exists, manufacturer exaggeration is rampant. Independent reviews are a more reliable guide, but in the end you need to 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. For one thing, HDTV is a wide-screen format. 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.

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 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.

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

This high-quality analog RGB connection is used primarily for computer connections.

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.

Also of the highest quality, HDMI is DVI plus a digital audio and control link. HDMI is the dominant digital connection interface for HDTVs today. 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 Disc 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. Of more importance to HDTV shoppers is how many HDMI inputs a TV has. Aim to get an HDTV with at least three or four HDMI inputs, to accommodate the multiple devices you're bound to accumulate.

HDMI inputs may include support for the Consumer Electronics Control (CEC) protocol, which enables CEC-certified components to send control information back and forth to one another. This arrangement can allow single-remote--or even single-button--control of functions involving multiple components, such as a TV, DVD player, and A/V receiver. Manufacturers tend to have their own names for HDMI CEC, such as CE-Link (Toshiba) and Anynet (Samsung). In many cases the CEC functionality is restricted to components from the same maker, which obviously lessens the benefit in a mixed-brand system.

Important: Resolution

Non-CRT displays, such as plasmas and LCDs, are fixed-pixel arrays, meaning 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 contrast ratio determine perceived picture detail.

<          3           >

© 2008 PC World Communications, Inc. All rights reserved