HD TV resolution explained

(Credit: Toshiba )

Is there such a thing as high def and higher def? CNET helps cut through the hype surrounding the various formats of HD resolution.

Resolution is the main reason why HD TV 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 HD TV 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-theatre maufacturers and trains professional video calibrators, the most important aspect of picture quality is contrast ratio, the second most important is colour saturation and the third is colour accuracy. Resolution comes in a distant fourth, despite being easily the most-talked-about HD TV spec today.

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 colour — HD TV looks more or less spectacular on just about any high-def television regardless of its size or the HD TV signal's resolution itself. The leap from normal TV to HD TV is so big that additional leaps in resolution — from high-def to higher-def, let's say — are tiny by comparison.

Nonetheless the HD TV 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.

The fix is in

For the rest of this article, we'll be talking about fixed-pixel displays. A fixed-pixel display is any HD TV 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:

  • No matter the resolution of the source material, whether VHS, DVD or HD TV, 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 HD TV. Or, as some unknown wag once said, "Garbage in, garbage out." There are two main HD resolutions in use today by Australian broadcasters: 1080i and 576p (although 576p would not be considered an HD format in many other countries). One is not necessarily better than the other; 1080i has more lines and pixels, but 576p 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 576p. True 1080p content is extremely scarce, however, and it will probably stay that way until more Blu-ray content is available here. The term 1080p today appears mostly in reference to the displays' native resolution, not the source.

Source resolution name Resolution in pixels HDTV Progressive scan Widescreen Networks/
sources
1080p 1,920x1,080 Yes Yes Yes Blu-ray and future HD-DVD players; PlayStation 3
1080i 1,920x1,080 Yes No Yes Channels Nine and Ten; Xbox 360
720p 1,280x720 Yes Yes Yes Some set top boxes output to this resolution
576p 852x576 Yes Yes Yes Channel Seven, ABC, SBS; Progressive-scan DVD players
Regular TV Up to 576 lines No No No All

Despite the obvious difference in pixel count, 576p 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 HD TV resolutions. It's especially difficult to tell the difference between 1080i and 1080p sources. The difference between DVD and HD TV should be visible on most HD TVs, but especially on smaller sets, it's not nearly as drastic as the difference between standard TV and HD TV.

HD TV 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.

Native resolution * Frequency Typical
TV types
1,920x1,080 Rare, but finally entering the Australian market in high-end televisions Flat-panel LCD; DLP, LCD, and LCoS projection
1,366x768 Very common in all screen sizes Flat-panel LCD; 50-inch plasma
1,280x720 Common in rear-projection but not flat-panels DLP, LCD, and LCoS projection
1,024x768 The most common plasma resolution 37- and 42-inch plasma
852x576 Still found in budget models 37- and 42-inch plasma

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 broadcast, 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 Australia, we're finally starting to see HD TVs with 1080p native resolution, which typically cost a good deal more than their lower-resolution counterparts. But as we've been saying, once you get to high-def, the difference between resolutions becomes much more difficult to appreciate. We've done side-by-side tests between a 50-inch 720p HD TV and a 50-inch 1080p HD TV 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're not telling you to ignore 1080p HD TVs. 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 colour, into their 1080p HD TVs simply because those sets are the high-end models. Today, however, the premium for 1080p is still pretty steep, and unless you're getting a very large set, say 60 inches or more, 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 HD TV 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 HD TVs generally do a good job of converting the signals, and because most HD TV is in motion and seen from a distance, as opposed to static text seen up close.

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TubbyJ posted a comment   

Why are the sides of TV images cut off the screen, and why do people (specially sports) look short and wide instead of the correct proportions?

 

Bazz posted a comment   

I can't get hd channels on my dvd recorder

 

cuckatoo posted a comment   

while buying a hdd recorder,the salesman told me that even though you have a hd tv you don't get the true hd experience till you put it thru a blue ray player. is this true?reply please!

 

unity posted a comment   

The aerial and aerial connectors can make a difference here. Call an aerial installer to get some measurements and change over to a "digital only" aerial if required. This type of aerial will help reduce inteference from analogue and FM sources

 

DimitriR posted a reply   
Australia

There is no such thing as a digital antenna. All these fly-by-night %u2018upgrade to digital antena%u2019 vans are con artists on crack.

 

Sara H posted a comment   

I just purchased a Samsung HD LCD tv and was very excited about getting it all set-up to enjoy. Not sure why but it doesn't seem to be picking up any digital channels and the analog channels are really fuzzy.
Could someone please explain what I have to do to get this tv to work properly? I have just used a normal tv cable connection but am not sure what sort of antenna is on the roof. Do i need to buy a set top box or a dvd player in order to get digital tv?
so confused!

 

Pastor posted a comment   

Samsung TV is now offering Plasma, LCD, and LED. What is LED?

 

MarkM2 posted a reply   
Australia

Pastor, LED Tv's are LCD sets that use LED technology as the source of backlight to the panel as opposed to the older sets that use fluorescent light globes. Televisions that use LED backlighting are much thinner than their fluorescent counterparts and generally use a lot less electricity to power them. Hope this helps. :)

 

buckdale posted a comment   

rodboswell's comment that the resolving power is no better than 2.4 pixels is made without any references. Also, his concept of resolution is not the commonly accepted definition. For example, my Sony Bravia Operating Instructions clearly states that the Display Resolution is 1,920 dots (horizontal) x , 1,080 lines (vertical).

 

MR.0BCB0F posted a comment   

(720p for almost all the game=XBOX360 PS3) (1080p blue-ray movie= PS3) (720p hd movie= XBOX360) main menu of xbox360 use any resolution but ps3 use 640p 720p 1080i 1080p. l use a 1680p x1050p pc 21" monitor on the 720p games streched and upscale .I prefer 32"720pHDTV or something smaller than 32" because of the pixel size ^_^ " soo if ur going for game i suggest you the 720p hdtv 16:9widescreen fast 2ms btw 720p game is better on 720pHDTV(its made for it) xD and streched on 1080pHDTV O_O...... not soo nice....and expensive for no big deal.....


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