For those who know about the math, optics, and/or practical aspects, I've heard that there is a range of screen sizes at typical viewing distances that is optimal for 1080p. For example, below a certain size screen (40"?) you can't tell 1080p from a lesser resolution. The question is, at what size screen with normal viewing distance could a person begin to notice a better pic with quad resolution compared to 1080p? 60", 65", 75" or would it need to be larger?

You mean something like this?
http://i249.photobucket.com/albums/gg212/hondar_2008/resolution_chart.jpg

nice

Or, measure the screen diagonally, and multiply by .84 (THX recommendation). For example, a with a 42" screen, you should be approximately 3ft away. :eek:

Keep in mind, this is more of a guideline, then an actual rule of thumb. Everyones perceptional abilities vary, which may allow some of us to view at a greater distance, and still reap the benefits of 1080p.

Or, measure the screen diagonally, and multiply by .84 (THX recommendation).

For example, a with a 42" screen, you should be approximately 3ft away. :eek:

Yah, that's crazy.

Correct me if I'm off, but isn't a whole lot of HD content still 720p? If so, there's less of an imperative to meet THX's 'ideal' 1080p viewing distance. Not that I would anyway, that is crazy close relative to screen size, no matter what anyone says.