by Arcadia Hudson

Created on: February 06, 2009

First there was black and white. Then color. And now the TV watching experience has gone high definition. Life-like pictures and CD quality sound are the trademarks of HDTV. But with talk of digital TV (DTV), analog TV, and other terms being thrown around, it's easy to get confused as to where high definition fits in.

To start off, digital TV does not automatically mean high definition TV. They are two different things. A TV that is not high definition can receive digital signals; it could be a TV with a built in digital tuner or that uses a converter box. DTV describes the type of television signal that is being sent. High definition describes the quality of the TV that is being watched. So it is possible to watch DTV on a TV set that does not show in high definition. On the other hand, it's the transmission of a digital signals that allows high definition to be possible. HDTV is a picture quality standard that fits under the spectrum of DTV.

So basically, when it comes to TVs that receive digital signals, there are the ones that can show high definition pictures, and then there are the others that can't. A TV can boast of a sharp picture and still not fit into the category of being true HD. HDTV is defined by aspect ratio, resolution, and frame rate.

Aspect ratio is the number of units high and wide the TV display is. For the standard digital television (SDTV), the aspect ratio is 4:3the same as analog TVs. For HDTVs, the aspect ratio is 16:9, which is a much wider picture.

Another element in the definition of HDTV is resolution. Resolution is measured by the number of vertical lines of pixels in the the television display. The more lines, the better the picture quality. The SDTV has 480 or 576 lines of resolution, but HDTV is made with 1080 or 720 lines of resolution. That's almost double the lines of resolution for a standard TV, and result is pictures with sharp detail.

Therefore, most basic definition of HDTV is a TV set that has 1080 or 720 lines of resolution and a 16:9 aspect ratio, but one last parameter, frame rate, is also important.

TVs work by redrawing pictures on the screen so rapidly, it creates the illusion of movement; kind of like animation. The frame rate is the number of times a complete picture is drawn on the screen per second. Pictures are drawn two different ways: by progressive scanning and interlaced scanning. Progressive scanning draws a complete picture by using all of the lines when refreshing an image. Interlaced scanning activates

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