Visible Resolution Limits

This diagram was presented by David Ranada in Sound and Vision. 
Look at this diagram and decide what size of screen do you need.

Shortly speaking: 
For 1080i/p display, if you want to see all details, the diagonal screen size shouldn't be smaller than the 2/3 of the watching distance.
If watching distance is 12 ft, diagonal screen size shouldn't be smaller than 92" for 1080 i/p resolution.