I've never run across a new technology that caused more confusion than HDTV. The consumer electronics industry took a simple entertainment device that most of us understand and turned it into a monster with enough specifications, whereases and wherefors to stump a convention of rocket scientists.
Hoping to get folks started, last week I offered suggestions for picking the right size set and deciding which HDTV technology is best for you. This time we'll talk about specifications - the geekspeak you need to know to make the right choice.
The spec bandied about the most - although it's not always the most important - is resolution. The term refers to the number of dots, or pixels, that make up the picture. By definition, HDTV has far higher resolution than standard TV with three to six times as much detail. That's what you pay for.
In computers, resolution is measured in horizontal and vertical pixels - for example, a 1,024-by-768 screen. In the TV world, it's the number of rows of dots that make up the image. That's essentially the same as the number of vertical pixels on a computer screen. In fact, many HDTVs can double as PC monitors.
Standard TVs have a resolution of 480 lines. Entry-level HD has at least 720 lines. Higher resolution sets can display 1,080 lines. Higher resolution is most important with large screens viewed at close distances. Otherwise, you may not be able to tell the difference.
Unfortunately, the industry threw in a kicker here. Manufacturers always add the letter "i" or "p" after the resolution, as in 720p or 1080i. Those letters stand for "progressive" and "interlaced," respectively.
An interlaced display uses two passes to light up the screen - one for the odd rows of pixels and one for the even rows. A progressive scan lights up each row in a single pass, producing less potential flicker and greater detail.
Screens with 1080p resolution are showing up in larger sets today, but you'll pay a premium for them.
Just as importantly, your broadcaster or cable company probably doesn't transmit a 1080p signal. The only way to get one is by hooking up a pricey, high-definition Blu-ray DVD player. So, for most of us, 1080p is overkill.
Other specs may be just as important as resolution. One to look for is contrast ratio, which is the ratio between the whitest white and the blackest black the TV can produce. The higher the contrast ratio, the better the TV is likely to render all the colors in between. You'll typically find contrast ratios that range from 300:1 for LCD sets to 10,000:1 for some plasma screens.
The bad news: There are several ways to compute contrast ratio, and everybody inflates the numbers a bit. So don't buy a set based solely on the manufacturer's specs. If you can, watch it in ambient light that's as close as possible to your home's.
Likewise, before you go to the store, measure the distance between the couch or chair you'll be sitting in and the location of the new screen. Distance plays a critical role in your perception of a TV image - and how comfortable you feel with screens of different sizes.
In the showroom, watch the TVs you're considering from the real-life distance and angle. If one store doesn't provide enough room to do this, find another that does.
And don't lose sleep worrying about technical specs. HDTVs will convert whatever signal they receive into the best image they can produce - a process called upconverting and downconverting. They're pretty good at it. What counts is how good it looks to you.
Once you're happy with a TV's output, it's time to consider how to get TV and audio signals into it.
By FCC regulation, new and larger sets must be HDTVs, which means they have a tuner that can capture an over-the-air, digital HD broadcast. This will be critical after February 2009, when broadcasters will switch to all-digital transmissions.
But there are still plenty of HD screens on the shelves - mainly older or smaller models - that don't have such tuners. These are generally referred to as HD-ready, HD-capable, or HD monitors.
If you plan to get your TV signal over the air, using an antenna (meaning no cable or satellite), be sure to buy a set with a built-in tuner. Otherwise you'll have to spend a few hundred bucks for an external HD tuner.
But if you have cable or satellite service, your digital cable box will be your HD tuner (hereafter, all references to cable will incorporate satellite TV service, too). You can hook up a basic cable or an analog box to an HD set, but you'll be getting the old low-definition image.
Assuming you've settled all this, it's time to look at the back of the set. You'll find the most complicated input/output panel you've ever seen. There are lots of ways to transmit TV signals from antennas, cable or satellite boxes, DVD players, iPods, cameras and other gadgets - one reason why even rocket scientists cower before HDTVs.
Basically, you want maximum flexibility. You may not find all these ports on every TV, particularly cheaper models. But you should be aware of what's available. If you don't want to memorize all this, you can find a clear, concise interactive HDTV explainer on the Discovery Channel's Web site at www.thehdguru.com
Component video: A set of three round ports labeled Y, Pb and Pr. These are typically used for video feed from HD cable boxes, tuners and high-end DVD players. Audio is carried separately. Look for at least two sets of these ports. Cables rarely come with the set, so if your cable company requires them, buy them at the store or make sure the installer brings them.
High-Definition Multimedia Interface (HDMI): This small, computer-like port carries the highest-quality digital video signal from HD tuners, cable/satellite boxes, and cutting-edge DVD players. Look for at least one of these.
Digital Visual Interface (DVI): Another digital video port using an Intel-based standard supported by some HD tuners, cable boxes and many computers. If you want to use your HDTV as a monitor, this is the easiest way.
Composite video: Old-fashioned RCA video ports, mostly yellow, used for standard analog signals from analog cable boxes. This is definitely a low-def signal and not what you bought your HDTV for. But it's an entry point for most VCRs, DVD players, iPods, camcorders, etc. Look for at least two composite ports - including one on the front of the cabinet.
S-Video: A step up from composite video input but definitely low-def.
RCA audio: Standard, analog audio ports (red and white) used by external TV tuners, cable boxes, VCRs, DVD players, iPods and other audio equipment. You'll find one set of RCA audio ports for each video input except HMDI. Look for audio ports on the front panel, too.
Coaxial: The familiar round port with the tiny hole inside designed for the broadcast antenna or standard video cable cord.
Optical Audio In: Fiber-optic system used by high-end HD tuners, DVD players and other top sound equipment. Turns sound waves into light for super playback on home theater systems. Optional unless you're a real tweak.
Coaxial Audio: Designed for high-quality digital audio signals from HD tuners, DVD players and other audio sources. For audio buffs.
Got all that? You can also find this information and the first HDTV column at www.baltimoresun.com/technology/