The wall of HDTV screens at the local electronics retailers calls out to me begging for my undivided attention in an unhealthy Poltergeist sort of way. On the retail sales floor all the pictures look super bright and it can be hard to distinguish which model offers the best grayscale shading and accurate color presentation without closer examination. As much as I prefer shopping online for everything, you don't really get a sense for which screen is best for your entertainment room without seeing it in person. Before you have the delivery guys drop a screen off on your doorstep, there's several key things you need to try before you buy.
Make Sure It's HDTV
Before you produce your plastic in the checkout line, make sure you know what you're buying. This seems like good advice for any purchase in the $1000+ price range, but few home electronics purchases are as confusing as HDTV. Many of the screens at the lower end of the price spectrum are actually Enhanced Definition TV screens, rather than being truly HD capable. EDTV is limited to 480p progressive-scan image quality, which looks better than standard definition and is the same resolution found in most DVD material available today. These screens can play HDTV signals from higher resolution sources like HDTV cable boxes or HDTV tuners by down-sampling the image from 720p or 1080i to 480p. HDTV-ready screens are exactly that, ready to receive an HDTV signal from an external source. These offerings rely on the cable box from your local provider or an external HDTV tuner to handle the signal processing before sending it to the screen and are capable of rendering HDTV resolutions. A true HDTV contains a built-in ATSC tuner/decoder capable of translating an HDTV signal at 720p or better resolution without requiring additional hardware. If you plan on getting all your HDTV content through a service provider, this may not be a major concern, but it's still something to consider in the purchase process.
For more on the HDTV resolutions, check my explanation of the HDTV standard over at InformIT.
Fullscreen Video on Your Widescreen
Most television broadcasts are meant to be shown in the standard fullscreen 4:3 aspect ratio of your old 27-inch television. Couple this with an archive of old fullscreen VHS and DVD movies and you may be watching a great deal of video that was never properly formatted for the current assortment of widescreen 16:9 aspect ratio HDTV screens. Consumer electronics manufacturers deal with this in different ways. My preferred method of viewing 4:3 video is in its original shape, which results in black bars appearing on either side of the image making use of approximately two-thirds of the widescreen viewing area. A second option is to stretch the 4:3 image to fit the full 16:9 screen. If stretching the picture to fill the entire screen is your preferred method of viewing, make sure the screen stretches both vertically and horizontally. Some budget HDTV screens only do a horizontal stretch, which results in picture distortion. The downside to stretching the picture is that you generally lose some portion of the top and bottom of the original image in the process of reducing distortion. If you want television broadcasts to fill the 16:9 screen, make sure the picture stretching feature does a stretch of both horizontal and vertical.
Standard Definition TV on a High Definition Screen
Unless your screen is dedicated to watching movies and the few shows broadcast in high definition, the majority of programming you watch will remain standard definition for the foreseeable future. To that end, an important factor in choosing an HD screen is how well it handles standard definition 480i video (digital cable signals are, in theory, progressive scan but translated to interlaced formats to accommodate the majority of televisions). HDTV generally reformats the content through a process known as upsampling or upconversion, which converts the interlaced content to 480p progressive scan, which is the same resolution found on DVD movies. A chip inside the television handles this conversion and some do it better than others. The most accurate upconversion processors are made by a company called Faroudja, which also packages its technology on boards from Genesis Microchip. Look for DCDi and TrueLife deinterlacing and image enhancement as part of a screen's feature set to make sure you are getting the best possible processing for standard definition video.
Truth in Picture Quality
There are two types of stores to shop at when choosing an HDTV. The boutique home theater companies with showrooms that attempt to emulate a true home theater, with the lights turned down and the screens calibrated for optimal viewing are one type of store. Wall of television retailers like Best Buy are the more common variety. While the boutique stores offer better lighting, you may pay more for the experience. Best Buy stores have gotten better in recent years, with regard to showing you what the television looks like. Instead of harsh store lighting, they've turned down the lights so you get a fairly accurate representation of what your screen will look like in a dark room.