David's Blog

My bro and I went to several places today looking at HDTV's. Probably one of the biggest complaints about HDTV's is how poorly they show standard definition (SD) television - regular television. The bigger the TV, the further back you will have to sit in order for SD television to look good

This web site has a nice calculator for figuring out how big a TV you should get if you want SD to still look good. You can skip the first input (distance to main viewing location) since that is not used in the calculation we care about. Just enter your screen shape (4:3 or 16:9) and screen size, then press "Calculate."

The result we are interested in is at the bottom under "Viewing Distance Based on Visual Acuity", "Maximum Viewing Distance for NTSC/PAL". This is the closest you should sit to see SD television. Sit any closer and you will start to see visual artifacts and bad-looking SD television.

I did a test with my current TV, a 4:3 32" Sony. I sit about 9' away from my TV. I am supposed to sit 10.2' away, according to the calculator. So I am too close. At 9', I can see some compression artifacts around text sometimes. Those artifacts would go away if I moved back a little more than a foot (which I can't without knocking out a wall). The visual artifacts are fairly minimal, but they are present.

SD is viewed as 4:3. To watch SD without stretching/distorting it on a 16:9 screen, you have to have the black bars on the left and right sides. This is the same as the mechanism called "letterbox" used to make a widescreen film fit on a 4:3 TV screen.

For 16:9 TV's, the calculator assumes you will be watching SD in a stretched/distorted (zoom) mode which fills the screen. I won't do this because I *hate* distorted video. If you want the results for undistorted SD on a 16:9 TV, you need to figure out the 4:3 screen size equivalent of your TV. This web site makes it easy. Go to "Screen Size Calculator", "Wide-Screen 16:9 TV." Enter your 16:9 screen size and press calculate. The 4:3 version of your TV is listed on the right as "Windowbox view diagonal."

For example, the TV I'm planning on getting is the 46" Sony LCD (KDL-46XBR3). The 46" 16:9 TV is the equivalent of a 38" 4:3 TV when showing SD material undistorted. Now I go to the Viewing Distance Calculator and use *4:3* for screen shape and 38 for screen size. The results say I should be sitting 12.2 feet away to see 4:3 content the best. Since my new set will be LCD, I should be able to put it closer to the wall than my CRT TV. That should increase my viewing distance to about 11 feet. So I'll be about 1 foot too close, just like I am now with my current TV. With a 46" 16:9 set, I expect SD quality to be about the same as my current 4:3 set.

Posted on July 15, 2006 6:20 PM | Permalink| Comments (1)