What are suitable TV sizes and viewing distances for couch surfing on a 1080p LCD HDTV?
Solution 1:
It would depend on your vision, but for me, 12 feet is way too far. I'm sitting about 2 feet from a "1080p" (OK, 1920x1200) 24-inch screen right now. Looks about right. So if the screen and pixels were twice as big, I could be twice as far back: 4 feet. To test it the other way, I also stood about 6 feet from this screen, and it was not comfortable reading at all.
That might even be a handy rule of thumb: for a 16:9-ish 1080p-ish screen, the viewing distance (for computer text like on a web page) is the same as the diagonal.
If you can't sit that close, some modern web browsers do a decent job zooming pages, and many programmers' editors allow you to choose the text size for the main editor (less so for the other on-screen tools). It seems counter-productive to reduce the desktop size to make the pixels larger: in this scenario, to double the viewing distance from 4 feet to 8 feet, you'd have to shrink the desktop from 1920x1080 to 960x540. Some dialog boxes get chopped off at 540.
You also want a TV that does (at least have the option for) "1:1 pixel mapping": i.e. each pixel generated by the video card -- connected digitally through DVI or HDMI or DisplayPort of course -- to be exactly one pixel on-screen. TVs are generally designed to crop off say 5% around the edges, called overscan, and zoom the picture slightly to fill the screen. That's because the edges are sometimes blank or have garbage pixels. Computers do not have this problem. Aside from the "slightly smudgy" pixels that result, the edges of a computer desktop often have critical things like taskbars and menus. To work around this, you can sometimes force the video card to shrink the desktop so that it fits inside the overscan, but that makes it even smaller.
Solution 2:
If you're viewing 1080p (1080x1920) resolution on a 40'' TV, you should be fine. Especially when it's an LCD. Again, if it's too small, just bring down the resolution on the same ratio, it should make things a lot more viewable. I know that if you hook up a PC sometimes to a large display like that, you'll definitely get a lot higher native resolution, but to able to view that higher resolution, you have to be like 5 feet away from the screen in order to read the text.
Solution 3:
Someone posted me this link which has a graph of screen size, resolution and optimal viewing distance.
I haven't investigated it in great detail, but it looks like it might contain some useful information for you.