It appears that some think this idea of a "proper viewing distance" for prints, and that the "apparent wide angle effect" is some half-baked idea. So I'm going to put in a few literature references for those who might have them.
Basic Photographic Processes and Materials (Stroebel, Compton, Current, and Zakia, 1990) - page 150, "The Wide Angle Effect"
Applied Photographic Optics (S. Ray, 3rd Edition 1992) - Chapter 23, "Perspective and projection", see 23.1.3 "Viewing distance" and 23.1.4 "Perspective distortions."
View Camera Technique (Stroebel, 5th edition 1986) - section 7.13 "Apparent Perspective Effects: Viewing Distance"
Controls in Black and White Photography (Henry, 2nd edition 1988) - p.235 "Proper Viewing Distance of Prints."
Enlarging (Jacobson and Mannheim, 20th edition 1969) - p.28 "The Problem of Correct Perspective," followed by "The Optimum Degree of Enlargement," and "Practical Magnification Problems."
The last, Jacobson, has perhaps the most "readable" discussion; here's an excerpt:
ps: in the event anyone wants to perform their own test - DO NOT use circles drawn on paper; this will not show the effect. (The wide lens sees the circles in a foreshortened manner, but the lens projection elongates them onto the film, cancelling the effect.) Only 3-D objects, such as people, or ping-pong/tennis balls, etc, will show the effect.We simply have to accept that we cannot achieve the realism of correct perspective with telephoto views. Fortunately this matters less in practice than might seem...
By similar arguments we can say that most people tend to look at wide angle pictures from too far away, or not enlarge the negatives sufficiently. That then leads to the exaggerated wide-angle perspective already mentioned. This is curable by simpling adjusting the magnification and final print size to the appropriate relationship for correct perspective. It incidentally also leads to a new way of looking at photographs: owing to the increased angle of view which the photograph subtends at the eye we can no longer take it in at one glance. The eye has to roam over the image - much as we scan a real scene in front of us.
This indeed greatly increases the realism of an enlargement from a wide-angle view. It is the reasoning behind wide-screen motion picture projection... This realism of perspective becomes equally impressive with giant enlargements of negatives taken with a wide-angle lens and used, for instance, as photo murals.