Here's a great article featured from CNET's website by David Katzmaier, called "HDTV Resolution Explained" http://www.cnet.com/hdtv-resolution/?tag=buttonWrapper;menu1

While this is a couple years old, it's still very well written and we've added a few comments in RED to reflect our opinions.

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.

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, (above 10,000:1 is approaching the limit of perceptability), the second most important is color saturation, (A monitor with good color saturation can display subtle color changes distinctly so that the human eye perceives the differences. If similar colors blend together or if colors appear dark, they are oversaturated; colors that appear washed-out and faded are undersaturated.), (above 1 billion colors is overkill and HDTV's today routinely are over 500 billion colors!), and the third is color accuracy, (which comes precalibrated on commercial TV's). Resolution comes in a distant fourth, despite being easily the most-talked-about HDTV spec today.  The exception is large format TV's 58" or bigger being viewed from typical family room distances 10-15 or smaller TV's viewed from very close distances.  Then resolution becomes more important.

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.

Nonetheless the HDTV landscape is littered with resolution discussions, in regard to both sources and displays, so a little knowledge of how they interact is a good thing.

Native resolution:

For the rest of this article, we'll be talking about fixed-pixel displays like flat-panel LCD and plasma. . .

. . . 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:

• 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.
• If the incoming source has fewer pixels than the native resolution, you're not getting any extra sharpness from the television's pixels.
  

HDTV source resolutions
If you read those three axioms closely, you'll see that source is everything with HDTV. Or, as George Fueschel first said, "Garbage in, garbage out." There are two main HD resolutions in use today by HD broadcasters and other sources: 1080i and 720p. One is not necessarily better than the other; 1080i has more lines and pixels, but 720p is a progressive-scan format that should deliver a smoother image that stays sharper during motion. Another format is also becoming better known: 1080p, which combines the superior resolution of 1080i with the progressive-scan smoothness of 720p. True 1080p content is extremely scarce, however, and none of the major networks have announced 1080p broadcasts. The term 1080p today appears mostly in reference to the displays' native resolution, not the source.  Dish has for its internet connected boxes, Video On Demand in 1080p. 

 Despite the obvious difference in pixel count, 720p and 1080i both look great. In fact, unless you have a very large television and excellent source material, you'll have a hard time telling the difference between any of the HDTV resolutions. It's especially difficult to tell the difference between 1080i and 1080p sources. The difference between DVD and HDTV should be visible on most HDTVs, but especially on smaller sets, it's not nearly as drastic as the difference between standard TV and HDTV.

HDTV display resolution
Now that we've considered the source, let's look at the televisions. As we mentioned above, all fixed-pixel HDTVs scale the incoming resolutions to fit the available pixels, throwing away information if they have fewer pixels and interpolating information if they have more pixels than the source. 

Technically speaking, all of these numbers are accurate and useful, but don't put too much stock in them. In the real world, it's difficult to tell the difference between native resolutions once you get into high-def. For example, despite the fact that a 37-inch LCD with "only" 1,366x768 pixels has to throw away a good deal of information to display a 1080i football game on CBS, you'd be hard-pressed to see more detail on a similar 37-inch LCD with 1,920x1,080 resolution.

The truth about 1080p
In the last couple of years, there has been a big influx of HDTVs with 1080p native resolution, which typically cost a good deal more than their lower-resolution counterparts. But as we've been saying all along, once you get to high-def, the difference between resolutions becomes much more difficult to appreciate. We've done side-by-side tests between two 46-inch LCD HDTVs, one with 1366x768 resolution and the other with 1080p resolution, using the same 1080i source material, and it was extremely difficult for us to see any difference. It becomes even more difficult at smaller screen sizes or farther seating distances--say, more than 1.5 times the diagonal measurement of the screen. We've reviewed a 37-inch 1080p LCD, for example, where it was impossible to see the separation between horizontal lines at farther than 45 inches away. . .

We're not telling you to ignore 1080p HDTVs. They technically do deliver more detail, which can enhance the viewing experience for more eagle-eyed viewers. Also, many manufacturers build other picture-quality benefits, such as better contrast and/or color, into their 1080p HDTVs simply because those sets are the high-end models. And given the continuing march of technology, we expect more and more 1080p models to become available at lower and lower prices. Today, however, the premium for 1080p is still pretty steep, and unless you're getting a very large set, say 58 inches or more, or sitting very close to a normal size TV, we don't recommend basing a buying decision on whether or not the television has 1080p native resolution.

This is the number of physical pixels the television uses to produce a picture. You may notice that few of the resolutions in the table match the HDTV source resolutions exactly. That's mainly because TV makers find it more cost efficient to make panels with the pixel resolutions in the table and then scale the incoming sources to fit the screen. It's true that ideally you'd like to exactly match the incoming source with the display's native resolution, but it's much less important in HDTV than in, say, computer monitors. That's because scalers in HDTVs generally do a good job of converting the signals, and because most HDTV is in motion and seen from a distance, as opposed to static text seen up close.

All fixed-pixel displays are natively progressive-scan, meaning that even if the source is interlaced, they'll convert it to progressive-scan for display. That's why, for example, you'll hear about a "1080p LCD" but never a "1080i LCD."

According to the CEA's DTV definitions, which, for obscure marketing reasons, actually include televisions that have fewer pixels than HDTV source resolutions in the section above.

Tips on Shopping for Plasma TVs

A plasma TV is no small investment for most consumers, so it really pays to know what all the fancy technical specs mean in layman's terms. And let's be honest, the local consumer electronics store isn't staffed with the most knowledgeable people. Hopefully the material below helps you understand what all the numbers, measurements, and comparisons mean so that you can select your TV with confidence.

You probably want to read about the differences between plasma and lcd or check our quick reference chart which compares plasma and LCD technology in a very basic manner. And within the plasma realm itself, you may not be aware of the choices between commercial grade and consumer models.

Another useful article clears up myths about plasma TV's.

And one of the most important articles a shopper may want to read targets pitfalls of internet shopping.

Diagonal Size: Measured from top left to bottom right corner. It's a matter of opinion I guess, but in general bigger is better.

Aspect Ratio: The aspect ratio is the ratio of the width of the picture to the height of the picture. Currently analog TV uses a ratio of 4:3. HDTV uses an aspect ratio of 16:9, similar to movie theaters. Why is this important? Because you have to consider what you're playing on a TV before you purchase. If your TV doesn't display the right aspect ratio then your screen will look funny; "letterboxing" means seeing big empty spaces on two sides of the picture, "anamorphic squeezing" means distorting the picture so that it fits the screen, and "pan-and-scan" means you're only seeing a part of the picture on your screen.

Pixel Pitch: The distance between pixel centers; or the distance between a pixel's centerpoint, and the centerpoint of the pixel above and pixel to the side of it. Why is this important? Well for smaller screen sizes, an LCD TV can fit more pixels next to each other than plasma. This increases the resolution of the picture. But then again, the smaller pixel size negatively affects larger LCD TV sets. The smaller pixel size means you can't just increase the screen and make the pixels farther apart. That would leave visible space, or a larger "fill factor" between pixels (an effect called "screen dooring"). So larger LCD televisions need more pixels and cost more to manufacture. And this also changes their native resolution. So that's why the best choice for smaller TV sets (36 inches or less) is normally LCD. But your best choice for a larger TV is probably plasma.

Contrast Ratio: The difference in brightness between full white and full black. So it's the brightest white compared to the darkest black that a screen can produce. This is listed as two numbers, and a bigger difference between the two is better; so 5,000:1 is better than 800:1. Why is this important? LCD televisions work with a backlight that is basically filtered to produce colors. So to produce black, an LCD attempts to filter this strong light completely, but it can only do so well. It can't make a pixel completely opaque. Whereas a plasma TV can simply turn the pixel off. Similarly a DLP can turn off the light giong to a pixel. So typically, plasma and DLP have a better contrast ratio than LCD. This means that your more dark and dreary DVDs - with scenes that take place in outer space or sequences that happen at night - really do look better.

Output Color: Whatever technology is used to change the color of a pixel, this is how many distinct colors that pixel can be. A larger number is better. Typically, because of the way plasma TVs work, they have the best range of colors. Why is this important? The picture can look much more realistic when more colors can be displayed, because there isn't as much of a "dropoff" between the color of one pixel and the color of it's neighbor. So the edges of an object moving on the screen just look more real.

Viewing Angle: How far to the side can you still see the image on your television screen. In this case, a larger number is better. With CRT televisions, as you walk to the side, you see a quickly degrading picture quality. Why is this important? If you have a large living room and all your buddies cram in there to watch the Superbowl^TM, the guys on the edges might not be able to see the picture as well. In general, plasma TVs have the best viewing angle but some newer LCD sets are designed with a front display panel that allows some pretty comparable viewing angles.

Scanning Frequency: n/a

Native Resolution: This is the resolution (pixels wide by pixels high) that a TV is designed to work with. So for broadcasts that don't match the native resolution, some converting needs to happen as the signal is displayed on the screen. Why is this important? Analog TV, HDTV, and DVDs all have different resolution. And they could change the resolution format in the future. If the native resolution of your television isn't as high as the signal being broadcast to it, then you won't get the clearest and best picture possible.

PC Signal Compatibility: n/a

Video Signal Compatibility: n/a

SD/HD Resolution: n/a

Input Terminals: n/a

Output Terminals: n/a

External Control: n/a

Special Features: n/a

Operating Conditions: n/a

Warranty: It may seem silly to have the definition for a warranty on here, but there are serious reasons for it. As with a lot of modern technologies, if your new television set (plasma, LCD, whatever) is going to fail, then that failure will happen pretty quickly; like in the first 2 years. There are a couple things to keep in mind about warranties. First is: are you really getting one? If you found the best possible price on the internet, then there's a good chance that the seller is not an AUTHORIZED RETAILER. This means that the manufacturer is not extending you any kind of warranty at all. Second thing is: does the warranty include in-home service? I mean, do you really want to disassemble and carry a big screen television back to the store or to a repair shop?

Power Consumption: n/a

Dimensions: n/a

Weight: n/a

See our full list of consumer shopping tips.

Question: Plasma or LCD?

As you consider your options in building the best home theater system possible, you will undoubtedly arrive at one major question: Which is better, plasma or LCD? Depending on your environment and what your goals are, the answer varies with each different application. Or click here for a quick reference comparison chart.

In general the rule we follow is that for larger sizes installed in the home (40 inches or greater), plasma is the better option. Because of weight and resolution, LCD is used at smaller sizes. For business applications, such as commercial signage or as a PC monitor, we recommend LCD. This is mostly in consideration of the static images being displayed on the screen (icons on your desktop, surveillance camera video, etc). The following article details how we arrived at those conclusions, through hundreds of installations.

Plasma displays more realistic color
Especially when you're talking about skin and earth tones, plasma monitors don't "neonize", or exaggerate colors like LCD's will. From our experience, LCD's do produce a nice color "popping" that especially looks good with computer graphics like Powerpoint presentations and video games. Colors are bright and vivid. But the accuracy of color reproduction in video is almost universally accepted as the plasma's biggest strength. We tell our customers to go to a local electronics retailer and look at the best LCD with images of people displayed on it. Look at that, and then look at your own arm to see how well the skin tones are depicted. You'll agree that the colors are much more accurate on plasma. But don't just take our word for it. If you're comparing metrics from different TV's, look at the number of colors it can reproduce. Plasmas will always come out on top by this measurement. Another stat that supports the measure of "color realism" is the contrast ratio, which plasma exceeds LCD on.

Plasma renders motion shots much more smoothly
Where you tend to see this is in the background of moving shots. In a football game, the camera is following the runner and the background moves behind the athlete. As those tiny blades of green grass move along quickly behind the player on an LCD screen, you will frequently catch some "twinkling" action with your eye. Why is this? Because the refresh rate on LCD is usually in the order of 10-12 milliseconds (compared to 6ms for plasma). In static or slower-moving images, this is enough to fool the eye into believing the movement is realistic. But when an image moves very quickly, your eye can catch the "in-between" frames when certain parts of the image are out of sync. Next time you're looking at an LCD, take note of the twinkling blades of grass or the blurry crowd behind that football player. As soon as the camera motion stops, the crowd will refocus and every detail on those blades of grass will reappear. By the way, you'll hear this condition referred to as "artifacting" on LCD sets. Plasma monitors simply work faster at refreshing the image, and therefore fool your eye better.

Plasma supports a better viewing angle
LCD technology works on the principal of filtering a bright white backlight into different colors as viewed from the front panel. Because of the way that this works, it means that light is focused to go through several layers of horizontal and vertical filters before it emerges from the screen. If you're sitting and looking at the TV straight ahead, then you're seeing the full effect of the focused light. But as you walk over to the side of the television, you see the image with less and less clarity; especially dark colors, because they are filtered the most. Plasma emits light through the front viewing panel in a different way, so it looks almost like a picture hanging on the wall. You can walk around until you're almost looking directly at the side of the television and you'll still see the image on the screen! This is the reason why you'll see people with higher-mounted LCD televisions actually tilted at an angle. Trust me, it looks really bad to have that monitor mounted above your fireplace at an angle so that you can see it well. This isn't something that you have to do with plasma. Not to mention when you and everyone from your block are crammed into the living room watching the Superbowl. Do you want to be the guy in the corner, leaning to the side and struggling to see what's happening? Although new LCD's are getting better, plasma still takes the cake.

When you need brightness in larger sizes, Plasma is the way to go
Unfortunately, not too many companies (especially LCD manufacturers) publish stats about brightness. Brightness is measured in "foot candles" or it's metric equivalent "candles per square meter", with a higher number being better. Why is the brightness a critical factor in selecting the right TV? If you have a well-lit room with lots of ambient light, you need a display that doesn't reflect the light in the room. If you've been doing internet research, you've probably read opinions that LCD is better when there is more ambient light. Traditionally, this has been the perception because of the beveled plastic screens on the front of the LCD monitor. The non-flat surface will reflect less light from around the room. But there are trade-offs to this non-reflective surface like the dimmer, washed-out picture when you look at it from any kind of angle. So for larger screen sizes, in brightly lit rooms, you'll get degradation of the picture towards the edges on LCD screens. On larger models, most LCD's run about 800 to 1,000 candles per sq meter. Whereas the newer plasmas are measured at 1,300 cd/m2.

What is "Contrast Ratio" and why is Plasma better?
Contrast ratio is the measurement of the brightest whites against the darkest blacks that a screen can display. So when plasma TV's boast of a 10,000:1 contrast ratio, that would exceed the 6,000:1 measurement in the best LCD's. And for larger televisions, the contrast ratio for LCD drops lower. Why is this? Just like with the viewing angle it's because of the different fundamental technologies behind plasma and LCD. Both LCD and plasma use many tiny tiny pixels to generate a picture across the screen. In an LCD, the pixels achieve different colors by filtering a white backlight in different ways. To make a black pixel, the LCD tries to filter the white light as much as possible. But even the best LCD's just can't filter the light completely. Whereas plasma TV's can actually turn a pixel completely "off", so that it emits no light at all! This leads to superior contrast ratios of course. But why is that important? Let's say you're watching a dark DVD, like a space flick or nighttime horror movie. On a television with less of a contrast ratio, various dark shades appear with sharp variations because similar colors appear as the exact same color. So you end up seeing this "color banding" effect, instead of smooth transitions between slightly different shades. On a plasma, someone with dark brown hair can stand against a black wall, and you can easily make out where the hair stops and the wall begins. Unfortunately on some LCD's hair and wall might appear to be the same color.

Cost makes Plasma better at larger sizes
Unless you're looking to spend the kids' college tuition on home theater, then you're interested in getting the best bang for your buck. The cost per square inch is significantly lower in plasma than in LCD televisions. A 50" plasma, superior in most functional respects to an equally-sized LCD, actually costs 20% less.

Plasma or LCD? Quick Comparison Chart...