12 feet is considered about right for a 50" RPTV unless it is one of the best performers. Then you can sit a little closer. I have customers sitting as close as 8 feet away, but they have Toshiba Cinema Series or Pioneer Elite models that have been calibrated correctly and they are watching high quality signals such as satellite or DVD. The widely accepted formula is to sit 4 times the screen height away. This works for widescreens as well as 4X3 sets.
As DTV takes over and the source signals and RPTV's improve, I expect this ratio to close up quite a bit. Perhaps down to 3 times the screen height.
Another quick way to get in the ball park, since it's hard to get screen height measurements off of manufacturers specs, is to use a ratio of three times the screen diagonal. (so, with a 50" diagonal screen you should sit three times 50" away, or 12 feet)
Hope this helps
MTN [Edited last by Mark Nelson on July 24, 2001 at 12:39 AM]