We have all heard certain plasma displays described as “enhanced” definition displays. “Enhanced” certainly makes these plasma TVs sound good … desirable even. Lucky for us there’s more to this than just clever marketing. Enhanced-definition (or ED) plasma TVs are actually better than conventional, tube-type TVs—not just slimmer and wider.

Resolution is the main reason why HDTV looks so much better than standard television. On a high-def TV displaying a high-def source, a million or more pixels combine to create images that appear sharper and more realistic than TV ever has before. Resolution isn’t the be-all and end-all of picture quality, however, and its numerous, well, numbers, can be incredibly intimidating at first. In this article we’ll try to demystify HDTV resolution and help you cut through the hype that surrounds all of those numbers.

What is an Enhanced Definition (EDTV) TV? It is simply a TV—be it a plasma television, or other technology that has 853 x 480 native pixel resolution. How important is resolution?

Not as important as you might think. According to the Imaging Science Foundation, a group that consults for home-theater maufacturers and trains professional video calibrators, the most important aspect of picture quality is contrast ratio, the second most important is color saturation, and the third is color accuracy. Resolution comes in a distant fourth, despite being easily the most-talked-about HDTV spec today.

Let me explain: Standard-definition (SD) TV—the sort most of us have been watching for years—has 480 visible lines of detail. This is the number of horizontal lines found on your TV screen. Remember, TVs are measured on the diagonal: The width of the screen changes, while its height remains more or less constant. Thus, it is the number of pixels on the vertical axis that really determines how much detail is visible.

In other words, once you get to high-definition, most people are perfectly satisfied with the sharpness of the picture. All other things being equal–namely contrast and color–HDTV looks more or less spectacular on just about any high-def television regardless of its size or the HDTV signal’s resolution itself. The leap from normal TV to HDTV is so big that additional leaps in resolution–from high-def to higher-def, let’s say–are tiny by comparison.

Like SDTV, EDTV contains 480 horizontal lines of picture detail, but the difference is that these 480 lines are displayed differently on standard- versus enhanced-definition televisions. SDTV utilizes a process called “interlacing” to display these 480 active lines of information. An interlaced picture is actually a single frame of video “painted,” line-by-line, onto the screen in two passes. On the first pass, all the odd numbered lines from top to bottom (i.e., numbers 1, 3, 5, … 479) are displayed. This takes 1/60th of a second to accomplish. In the next 1/60th of a second, all the even lines are painted. So, it takes exactly 1/30 of a second to display a full picture at 480i (”i” for “interlaced”). The refresh rate of such displays is 30 Hz.

With EDTVs, these 480 lines are displayed progressively, meaning all the lines are “painted” onto the screen sequentially (1, 2, 3, … 480) in one pass as opposed to two. Which essentially means that more information can be displayed with progressive scanning since there is not 1/60 of a second lag between “takes.” What would otherwise take 1/30 of a second to be displayed using interlacing can actually be shown in half the time progressively. Progressive-scan formats provide full vertical resolution at all times, at a refresh rate of 60 Hz. Hence the enhanced picture quality that comes with progressive scanning.

Which is why EDTV has been called by some the biggest advance in video quality since color TV. Now, HDTV plasma is taking center stage as prices come down quickly on LCD and Plasma TVs. The simple anwer on what a HDTV plasma would be is 1024 x 768 resolution or higher (1366 x 768 is common on 50″ plasma, and 1024 x 768 resolution is common on 42″ plasma TVs).

Native resolution: The fix is in
For the rest of this article, we’ll be talking about fixed-pixel displays. A fixed-pixel display is any HDTV or monitor that uses pixels to produce an image, including flat-panel LCD and plasma screens as well as rear-projection microdisplays and front projectors that use DLP, LCD, or LCoS technology. We’ll ignore non-fixed-pixel displays; namely, direct-view and rear-projection CRTs, because they treat incoming resolutions differently than their fixed-pixel cousins do–since they don’t use discrete pixels, their specs are much more difficult to pin down.

All fixed-pixel displays have a native resolution spec that tells you how many pixels the display actually has. Native resolution is the absolute limit on the amount of detail you’ll see.

Fixed-pixel displays follow a few basic rules:

• If the incoming source has fewer pixels than the native resolution, you’re not getting any extra sharpness from the television’s pixels.
• No matter the resolution of the source material, whether VHS, DVD, or HDTV, a fixed-pixel display will always convert, or scale, it to fit its native resolution.
• If the incoming source has more pixels than the display’s native resolution, you will lose some visible detail and sharpness, though often what you’re left with still looks great.