How To Buy Guide - TV's Guide

Between HDTV and the move to digital, television has been going through big changes lately, so we'll start with trying to explain what's different about new TVs.

Digital versus Analog

Since the dawn of television, we've been relying using analog signals to access free "over-the-air" broadcasting. In the near future, however, that's set to change: in early 2006, Congress passed a bill that will require television stations to switch over completely to digital broadcasting in February 2009. Congress also required that by March 2007, all TVs being made or imported into the US should have a digital (ATSC) tuner. Those using older analog sets shouldn't worry – there's a subsidy program that will go into effect in 2008 to help you afford the cost of a digital-to-analog converter box.

If you're looking to buy a new TV, whether it's an SDTV or an HDTV, be sure to check and make sure it has an ATSC tuner (on the PriceGrabber site, make sure it says "ATSC (Digital)" or "HDTV" under Broadcast Format on the TV's Product Details page). It'll save you the hassle of getting a digital-to-analog converter box once 2009 rolls around.

(Of course, if you subscribe to cable or satellite, you most likely don't have to worry about this issue...but if you plan to get your broadcast television via antennae, be sure and look for a TV with a digital tuner.)

Types of Displays: Resolution & Scanning

Next, we'll look at resolution, which measures how detailed a TV's picture is. We'll illustrate the in's & out's of resolution looking at two types of displays:

Standard-Definition TVs (480i resolution) – These televisions (also called SDTVs) display 480 scan lines of video on the screen – this is the way we've been watching television since the 1950's. The "i" in "480i" stands for interlaced scanning, which means that the TV displays the image in two passes. The first pass draws the odd-numbered lines, and the second pass fills in the even-numbered lines on your screen.

SDTVs have two things working against them – first, because of the interlaced scan lines, images onscreen often develop jagged, less-clear edges. This happens because when images are moving on an SDTV screen, often the image will have moved in the split-second between the first and second passes, leaving visual artifacts behind. (Of course, since SDTVs display video at 30 frames per second, we're talking fractions of a second here...but when you put it all together, it adds up to a much less-clear picture.)

Second, because they only display 480 lines on the screen, SDTVs don't scale well. When you look at a big-screen SDTV, the scan lines are much more obvious, yielding a less-crisp picture. 480i is fine for smaller TV's...but once you get above, say, 23 inches, there are better options to be found.

Enhanced-Definition TVs (480p resolution) – To solve some of the problems found with SDTVs, manufacturers came up with EDTVs, which display video in 480p (480 lines, progressive scan) format. Instead of rendering images in 2 passes, a progressive scan TV builds the image in one pass, one line at a time, yielding a crisper image without the artifacts common in SDTVs. By rendering all 480 lines in one pass, the EDTV also can display 60 frames of video per second, instead of the usual 30 frames per second – this gives you much more realistic motion and makes moving images appear a lot sharper. To most people looking at the same image on an SDTV and an EDTV, the difference in image quality will be easy to see.

Most EDTVs are cost-effective, and provide a noticeable improvement in picture quality over SDTVs. But they still don't solve the big-screen problem. Just like with SDTVs, if you're looking for a TV under 23 inches, you'll probably be fine with an EDTV. If you want to go bigger, however (or plan for the future, as more and more high-definition broadcasts become available)...you should look for an HDTV.