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Demystifying HD: A Primer on High Definition Television

by Chris Taylor
10/05/2007

About a year ago, a friend of mine burst into the living room of my apartment, incredibly excited. “Guess what!” she said. “I got a new laptop!” I’d recently helped her fix a problem with her previous computer, so I’d become the de facto authority on technology. “It has an Intel 3.2 gigaherz Pentium 4 processor with Hyper-Threading Technology!”

At last, she left a pause for me to respond. “That’s great,” I replied. She stood there for a moment more, a toothy smile frozen on her face. I said, “You don’t know what any of that means, do you?” “Nope,” she replied, just as ecstatic as before.

Electronics companies throw so many new terms at their consumers these days, it’s a wonder anyone ever knows what they’re buying. Even the store clerks selling it can’t explain it to their customers half the time, either because they can’t put it into plain English or because they simply don’t know the truth themselves. Yet somehow we’re expected to buy computers, cell phones, televisions, headphones and mp3 players without understanding anything about them.

Perhaps the most prevalent of these terms right now is “high definition.” The phrase is usually used in the context of television, HDTV. The average consumer is presented this ‘High Definition’ technology, persuaded that it’s somehow better than the alternative, but not told how it’s better. The words echo the Hi-Fi stereos of the 60s and 70s, as if our old televisions are like hand-cranked phonographs.

Contrary to the conclusions one might draw from the ineffectual efforts of cable and satellite providers, as well as the manufacturer of TV sets, to supply their customers with information, the differences between high definition and standard definition are quite simple. It’s all about resolution: the number of individual dots (usually called pixels) of single colors that, together, make up a whole picture. High definition has more pixels (little dots) than standard definition, thus creating a sharper picture and a greater variation in color.

In the US, standard definition television has a resolution of 640 horizontal pixels by 480 vertical pixels. This means that any standard TV set, TV signal, or DVD has a resolution of 640 by 480 pixels. If you’ve ever heard anyone say ‘480i’ or ‘480p,’ the number of vertical pixels is the number to which they’re referring.

With the advent of the high definition standards, that resolution has increased drastically. There are two different standards for HDTV. One is called 720p. It has a resolution of 1280 horizontal pixels by 720 vertical pixels. The other is called 1080i. It has a resolution of 1920 horizontal pixels by 1080 vertical pixels. Put simply, HDTV shows up to six times as many dots on the screen as standard TV, allowing for significantly more detail and color variation.

Another important thing to consider about high definition (HD) versus standard definition (SD) video is how this applies to say, computer monitors. Good news: the unit of measurement - pixels - is the same.

When buying a computer monitor, if it claims be “HD” capable, make sure it has a resolution of at least 1280 x 720. Otherwise, the manufacturer is trying to pull a fast one on you. Similarly, if you’re in the market for an HDTV, make sure you check to see if it supports at least 720p. Don’t be fooled just because it’s widescreen - the size of the screen doesn't necessarily mean the television has a high resolution. Don’t be afraid to ask questions and demand accurate answers before you make your purchases.

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