HDTV Basics

As you know, HDTV stands for High Definiton Television. A higher definition means a sharper, more realistic picture, with more details, better colors, and smoother action than a regular TV. How does an HDTV manage all this? It all starts with the dots:

Every picture on a TV screen is made of thousands of little colored dots, also known as pixels. A regular TV screen has 480 rows of pixels and 720 pixels in each row, for a grand total of about 350,000. A high-end HDTV has 1080 rows and 1920 pixels per row, for a total of about 2 million! That's a lot of information. To get a feel for the difference, open your browser window all the way and click on the image below:

The difference on an actual HDTV is far more dramatic, but this gives you a rough idea of the difference in sharpness and screen dimensions. Check out the details, like the sagebrush, the cliffs in the background, and the wider field of view in the HDTV image.

Scan Type (progressive vs. interlaced)
A TV set uses pixels to "build" the picture on the screen, and it can do this in two different ways. In a progressive scan, the whole image is built, then erased, then the next image is built. Computer monitors, movie theaters, and most HDTV sets use this method.

In the 1930s, the interlaced scan method was invented to improve the image quality without increasing the bandwidth of the broadcast. An interlaced display builds half the image (the odd rows of pixels), then builds the other half (the even rows). Between the 1930s and the 1970s, TVs with progressive-scan displays could not work fast enough to match the smoothness of the interlaced displays.

Now that TV technology has improved in all areas, progressive displays are now even smoother than interlaced displays, especially when watching fast-moving images like football games.


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