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Home > January 2008 > HDTV's Explained
HDTV's Explained 
Televisions have been around since the late 1930's. Today there are households that have multiple TVs. Until recently television has been displayed at 480 lines on the screen. HD TV is either 720 lines or 1080 lines. HD channels on cable or satellite are shown at 720p or 1080i (1080p is not available yet due to bandwidth restrictions), currently HD DVD and Blu-ray, along with some new gaming systems, are the only sources that output in 1080 right now. An up scaling DVD player will output close to an HD DVD player.
There is two ways to output 480, 720 and 1080, in interlace or progressive scan (1080i, 1080p). Interlace is when the picture is created, outputting every other line on the screen, then passing again to create the lines that were skipped. Interlaced pictures need to be deinterlaced and shown on the TV. LCD TV's and screens larger than 42 inches, in LCD and Plasma format, and watching sports, are when the progressive and interlaced make the most difference. Progressive scan is when the whole picture is displayed at the same time. You will really notice the difference between interlace and progressive in fast action movies or sports.
All HD TVs will output in 720p. For the moment 720p is all you need to get the benefits of HD cable or satellite, or an up scaling DVD player. If you have the funds, you may want to go all out and get a 1080p television. That way when the Bluray or HD DVD players go down in price or some other HD technology comes out, you will have a top of the line product.
You will want to find a TV with a fast response time (less than 10ms), and a TV that has either 1,920 x 1080 pixels (1080 i/p), or 1,280 x 720 pixels (720 i/p). A TV with 1,280 x 720 will not be able to display in 1080p. A brightness of 400cmd or higher and a native contrast ratio of 800:1 are also some specifications you want to look out for. Native contrast is the range between the black and white colors at any given time. Dynamic contrast is the range between the black and white colors over time. (Article from Viewsonic, An Article on a Message Board) Some television ads will display a high contrast ratio, which may be a the dynamic ratio. You want to look for a native contrast ratio of 800:1 - 1200:1. If the contrast ratio is said to be 8000:1 or 10000:1, it is the dynamic ratio. It is somewhat of an advertising ploy, not that the number doesn't mean anything, but you should be more interested in the native ratio over the dynamic ratio. Native, or static, and Dynamic ratios cannot be directly compared, although some advertisements make it seem that way.
If you have very technical details, a pixel pitch less than 0.6mm is also something to look for. The pixel or dot pitch is the distance (in millimeters) of the cells that are the same color. Each pixel has a red, green and blue cell. The smaller the dot pitch the closer the red cell of one pixel is to the red cell of another pixel. The smaller the dot pitch, the sharper the image.
There is a new technology, some TVs are coming out with refresh rates of 120Hz. It still is pretty new and there are not many articles on this, but from what is out there, it may make the picture look more 3D and smooth. At the moment the TVs that have 120Hz refresh rates are almost double the current 60Hz TVs. The refresh rates have correlation to the response time (in milliseconds). Click here to read an excellent article out 120Hz HDTV's.
I personally have the GV47LF, 47" LCD television from Vizio (Samsung makes Vizio). Click here to read my review on this TV. The TV has an 8ms response time, 1080p, 2 HDMI and 2 component inputs (HD inputs), 500cmd brightness and a 800:1 native contrast ratio/1600:1 dynamic contrast ratio (you can turn dynamic contrast on or off).
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