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The benefit of HDTV nobody else will tell you about

technofile  by al fasoldt

Columns and commentaries in a life-long dance with technology
 

Simple gray rule


The benefit of HDTV nobody else will tell you about
 

By Al Fasoldt

Copyright © 1993, The Syracuse Newspapers

When TV experts talk about the benefits of the television set of the future, they point out that high-definition sets will offer a sharper picture and show more detail. But that's only half the story.

The other half is probably more important to the average viewer. You'll finally get to watch a TV that doesn't flicker.

I found out about flicker when I was a kid watching Gillette's "Friday Night Fights." My dad never missed a round, and the rest of us always joined him in front of the little oval tube in the living room. To me, boxing was both boring and dumb, and so I came up with a couple of diversions.

My favorite was waving my fingers in front of my eyes while looking at the TV. If I did it just right, all the motion seemed to stop. My fingers looked as if they were frozen in place.

I had come across a stroboscope, but I didn't know anything about it at the time. All I knew was that the TV obviously flickered. So if I moved my fingers at the same rate that the picture was blinking on and off, they didn't seem to move.

That was more than 40 years ago. Despite the many improvements in television over the last four decades, the flickering TV is still with us. In some ways, it's the only thing that's wrong with our present TV system.

Flicker, of course, describes something that blinks many times a second. Old home movies, the kind taken with 8mm film, suffered from too much flicker, and fluorescent lights that are going bad do, too.

But the most common source of flicker is the standard TV screen. It all came about at the dawn of TV design, when engineers had to find a way to get around the crude electronics of early TV tubes. These tubes weren't able to draw an entire screen image in one-sixtieth of a second—the period that each still picture is flashed on the TV screen—so the engineers devised a halfway method.

Their solution was to show half the picture in each sixtieth of a second. The electron gun that draws the image fills in all the even-numbered scan lines, turns itself off, and then goes back to the top of the screen and fills in all the odd-numbered lines.

This half-and-half picture drawing is called interlacing. Supposedly, your eyes are fooled by this sort of trickery, so you end up seeing the entire picture. But in fact, what you actually see—or what you sense, even if you can't see it directly—is a picture that is not steady.

If you're not sure you can notice this flickering, you should be able to spot it easily if you look to one side of the TV, especially when the images have a bright white background. Our eyes are more sensitive to flickering when the light comes from one side.

Another way to spot the flickering is to go to a department store that sells both TVs and computers and compare what you see on a TV screen with the image on a modern color computer display. The computer image will seem very stable compared with the TV picture—because the computer image is not interlaced.

It's almost a sure bet that TVs will lose this last vestige of 1950s technology when HDTV sets are available here in the next few years. Designers of some of the proposed HDTV systems have tried to point out that interlaced HDTV sets would be cheaper, and some have suggested that consumers would not miss what they haven't seen. But most of the proposed systems rely on flicker-free, non-interlaced displays, which are necessary if HDTV sets are to be used to display easy-to-read text—a full page of a newspaper, for example - as well as pictures.

Besides, modern electronics can handle the job of drawing a complete picture, rather than half of it, just as inexpensively as the old half-and-half method. If there's one sure thing we can say about electronics over the past 40 years, it's that high-tech items get cheaper and better at the same time. No videophile can resist that combination.


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