There are many HDTV options out there and I wanted to talk about some elements of HDTV that potential purchasers might want to be aware of. Note that I found a great source of definitions here on CNet.
Here are some important definitions:
Like in the world of digital pictures, higher resolution is better because the more resolution the more the detail. The HDTV standards define resolutions as follows:
- 852×480 (480I) — This is the resolution of standard definition TV
- 1280×720 (720P) — This one of the resolutions of HDTV
- 1920×1080 (1080I) — This is another HDTV resolution option.
- 1920×1080 (1080P) — This is the highest resolution HDTV option available. No one is currently broadcasting in this and it is unclear if anyone will.
One more definition — I vs P
All of the resolutions above include the letter I and P. These letters describe how the picture on the TV screen is updated. The two terms stand for “Interlaced” and “Progressive Scan”. Before defining the terms it is important to remember that the a TV picture is made up of many horizontal lines and these two terms define how each individual line in the picture is updated.
Interlaced — This approach dates back to when TV was first introduced. Original TV technology did not have the ability to refresh the entire TV picture at once and so the interlace approach was created. What this does is refresh half of the lines on the TV screen at a given time. Thus it would first refresh the odd lines then even and then odd etc…
Progressive Scan — This technology has its derivation from computers. Computer technology is much newer than TV technology and so was developed when screen technology was more advanced. With Progressive Scan all lines on the screen are updated simultaneously.
Why should you care? At the same resolution, you will typically find the progressive scan does a better job with rapidly moving images and delivers less visual artifacts. Thus all things being equal, you would always prefer progressive scan over interlaced signals.
Which delivers the best picture, 720P, 1080I, 1080P?
The resolutions above are all the options available with HDTV, and the question comes up about which is the best. The clear answer is that 1080P provides the best image. It is the highest resolution and is progressive scan. The problem is that there are few video sources that can provide this signal. (The exception is the new HD DVD players — Blu Ray and HD-DVD).
The most HDTV common resolutions are 720P and 1080I. The question you may ask, is which of these is better? The answer is not entirely clear. 1080i provides higher resolution, but it is interlaced which is less good for active movement. 720P is lower resolution, but it provides the progressive scan. In the end, the choice of 720P or 1080I is determined by the broadcasters. I believe that ESPN uses 720P and I am not sure about Fox or NBC.
It is important to note that all of today’s HDTVs support 720P and 1080I. These TVs include technology that will automatically adjust the TV to the different video formats. Thus you should not be concerned about supportting the different formats.
What about native TV resolution?
This is an important question. As mentioned above, modern HDTVs support both 720P and 1080I. The thing about HDTVs is that all TVs have a native resolution. That is the resolution that the TV can display without modifying the signal. The native resolution will vary depending on the TV. The most common HDTV resolution is 1280×720. You may ask “if that is the resolution, how can you display 1080I?” The answer is that the TV has a special chip that can convert 1080 signals in the 720 signal that the TV natively supports. This works great, but it also means that you do not get the full benefit of 1080 signals since you are still only displaying 720 resolution. Newer and more expensive HDTV’s support the full 1920×1080 (1080) resolution, and these are the preferred option if you have the budget
I am buying a TV which should I choose?
If you have the budget then I would suggest a full 1080 HDTV. If your budget is more limited then a 720 TV should be fine. Certainly it will not deliver the same resolution as the 1080 models, but for the average viewer 720P is more than adequate.