Size Up Your Viewing Requirements
Finding the perfect HDTV starts with taking a good look at the room where you're going to put it. The recommended viewing distance for HDTV is less than half what it is for standard TV, so you'll need to either go bigger or move in closer when you make the switch. The distance from your eye to the screen should be about 3 to 3.5 times the diagonal screen size. For example, a 42-inch HD monitor looks best at a distance of about eleven feet. Sit any closer and you're inviting distortion effects; too far back and you're missing the high-def details. So get out your measuring tape, and write down your approximate viewing distance in inches. Divide by three, and that's the approximate screen size you should be shopping for.
Check the lights
Along with viewing distance, you should consider the room's lighting, and how the set will typically be used. Will it be viewed more during the day, at night, or a combination of the two? Some types of monitors, such as projection units, work best in a darkened room - the darker, the better. If the set is going to get a lot of daytime use, or operate under varied lighting conditions, it's important to pick a model that will perform well in brighter light.
Consider the source
What you'll be watching is also a factor. If you're a movie buff, you'll want a set that does a good job at displaying black - otherwise night and interior scenes will lack shadow detail. LCD and plasma sets, while they're getting better, still tend to underperform in this area. But if you're a big sports fan, black performance is less important than getting a bright picture that looks good in daylight - and that's something LCD and plasma sets are quite good at. Finally, if the set is going to be plugged into a gaming console, or if you're going to leave it tuned to the same channel for days at a time, you should avoid displays that are vulnerable to "burn-in" damage, like plasmas and CRTs.
Resolution and aspect ratio
The highest HDTV resolution currently available is "1080p," but do you really need it? Here's the quick story on resolution numbers:
480i is old-school broadcast TV. 480 lines of vertical resolution, 30 frames per second. Also known as SDTV (standard definition). The same TV your grandfather watched.
480p has the same number of lines, but twice the frame rate, making action sequences seem smoother. When you watch a DVD on a progressive-scan player, this is what you're seeing. TVs that can display 480p are sometimes marketed as "EDTV," or enhanced-definition sets. It's better than standard TV, but still not HDTV.
720p and 1080i/1080p are all considered true HD resolutions. The differences lie in the number of vertical lines displayed (720 or 1080) and whether the signal is interlaced (30 frames per second) or progressive (60 frames per second).
Now, most people can easily spot the difference between 480 and the higher resolutions, but once you enter the realm of true HD, the differences start to get more subtle. When people express a preference at all, it is usually between the two frame rates, with the faster "p" resolutions offering slightly smoother action sequences. Keep in mind that all HDTV signals – broadcast, cable, and satellite – are currently transmitted in either 1080i or (less frequently) 720p. So unless you’re watching an HD-DVD or Blu-ray disc, or you’re hooked up to a PC or high-end gaming console, you’re not really getting the true 1080p experience. Nevertheless, 1080p displays are widely available and offer the highest quality viewing experience, now and in the future.
As for the screen's aspect ratio, it's really a no-brainer. Virtually all HDTV programming is broadcast in the 16:9 "widescreen" format. Sure, you can still buy a set with the old 4:3 "square" format, but why would you want to when the world's going widescreen?