According to the engineers that set up NTSC it's 8 times the heighth of the screen with a fudge to 6 times on RPTV due to defocusing at the screen to blend the scan lines. And 4 times for progressive scan sets.Actually it was 10 times but improvements in power supplies and screen shape (less overscan needed) have changed that.
I would say pretty much the same thing a bit differently: 3 times the diagonal for NTSC sets, and 2 (or less) for HD-ready sets at 480p or better.
This happens to work out almost perfectly for a 16:9 set that shows 480p or better at 16:9 but NTSC at 4:3. Turns out that you are sitting farther from the 4:3 image, which is what you want. Of course, it is possible to watch a 16:9 show at poor resolution, and a 4:3 at high resolution, but one has to go with the probabilities, or keep moving one's chair.
I know this is an old thread. I have been searching threads for a recommendaion on distance from a screen. I found this old thread. I have the same question. The only thing I found was this table from Crutchfield. This suggests a larger screen that we were considering. We have 12 1/2 feet to screen from our couch and were considering a 48 HDTV screen. This suggest a 58" screen which we are concerned is too big for the room. And secondly, I know with HDTV you want to be the same level as the screen or the picture may appear darker. What about viewing from the sides?
Can anyone verify this information from Crutchfield, how they come up with these?
The charts below are general recommendations. For analog TVs with 4:3 aspect ratio, the suggested viewing distance is equal to the screen size (measured diagonally in inches) multiplied by 3. For HD-capable TVs, multiply by 2-1/2.
I think the HD numbers you list are maximums. With a high-quality image, such as from a progressive-scan DVD player, you may want to sit closer, to get more of a movie-theater-like experience.
Thanks for responding. If 2.5 is the max, what is the suggested lower end? So would you suggest a safe range for HDTV of 2 to 2.5 times the diagonal size as the viewing distance?
Any thoughts on the distance from the sides to be able to view?
For scaled DVDs, you want to be sitting 1.5 to 2 screen widths from the screen (I find 1.7X to be a nice compromise for better and worse DVDs). At 12', this translates into a 6 to 8' wide screen (81-108" 16:9 diagonal).
1080 line HD requires a viewing distance under 3.2 screen heights for people to fully resolve the picture which would mean an 80x45" screen (90" diagonal) at 12'.
If you're stuck with interlaced video, about twice as far works as in 3 diagonals (4 widths, 5 heights).
With 27", the numbers from the above would be 32"-43", 39", and 81".