DTV Primer

Chris Llana, Editor



Widescreen Diagonal Measurement - How Does it Compare to NTSC?

July 13, 2006

Okay, so your old analog TV is on its last leg, and you want to replace it with pretty much the same size digital set. Do you buy a set with the same diagonal screen measurement?

Probably not a good idea.

Let's say your old set is a 27 incher. The area of its screen is about 350 square inches. Now, if you bought a 27" widescreen TV (if you could--they're mostly 26"), the screen area would be about 312 square inches (or about 89% that of the 4:3 set).

If we look at screen height, which may be a better indicator of how we perceive how "big" a screen is, the difference is more pronounced. To wit, the 27" 4:3 set's screen is 16.2 inches tall, while the "same size" widescreen TV's display is 13.2 inches high (81%).

That's a full three inches shorter!

All of this calculating was prompted by a call from my elderly mother reporting the premature demise of the 25" analog TV in her bedroom. Of course it would have to be replaced by a digital set, but what size?

Certainly nothing smaller. (She sits far away.) But she was happy with the old size and wanted something comparable, and nothing extravagant!

So off to the store I went, looking for something around 26". But those looked too small. The 30" models looked more appropriate. So then I went to the library and did more research on manufacturers and then home again to do more internet research.

What I ended up with was a recommendation for a 32" LCD flat-panel TV. Hauling a big Sony CRT widescreen TV up the stairs and finding a place for it on the dresser was not an attractive option (heading up toward 200 pounds).

The Hewlett-Packard (HP) model I was recommending cost about $1200, something my parents would likely see as exhorbitant for a TV, since the old 25" set cost about $250. But it was the right TV, if only the justification was sound.

The weight was certainly right, at 43 pounds. And only a few inches deep--11" including the base.

But 32" is a much bigger number than 25", the size of the set being replaced. So my recommendation to go from 25 to 32 sounded like getting a much larger TV. However, widescreen displays are NOT the same, and comparing diagonal measurements is the old apples versus oranges thing.

My mother watches a LOT of daytime TV, and a lot of that is still presented in 4:3 aspect ratio. On a widescreen set, that sort of remaining 4:3 programming will have vertical bars on the left and right (unless stretch modes are employed). So to get the same size picture on a widescreen display as your old analog TV, make sure the height of the screen is the same.

With regular widescreen programming, people and other things on the screen will look to be the same size (height) on the widescreen set as what you were used to seeing on the analog set; you'll just get more of those things (horizontally) on the widescreen display.

As it turns out, the height of a 25" analog TV screen is about the same as a 31" widescreen display. Since 31" is not a standard size, and we don't want to go smaller, a 32" digital TV is the correct replacement for that old 25" set.

If you want to replace a 27" analog TV with a comparable size digital set, get a 34" widescreen set.

32" analog set? Try a 40" high-definition TV as a "same-size" replacement.