well jani, i appreciate the effort to track down where myhrvold went wrong. i agree that even the titled are 'entitled' to make mistakes (though if someone politely points out that you're wrong, and you rudely insist you haven't made any mistake, well, that's a different case). i realize that the 1.5 gaussian blur radius factor was probably based on the 1dsII, but i don't have one handy to do that test (my old 20d though, with even greater pixel density than the 1dsII, gives remarkably similar results to the 5d, better than the example on the cambridge site shows--not sure what is going on with that and can't do further tests, as i gave the 20d to my brother. but we don't know what lens the cambridge site used, and we don't really know much else--raw or jpg, noise reduction or not, etc, which may have affected that image. i don't deny that the 20d captures less detail at f/22 than the 5d--i just didn't see the very dramatic kinds of effects illustrated on their textured fabric). what i found interesting was that the results of a 1.5 radius blur on the f/8 5d image look exactly the same as the image which myhrvold first suggested, ie that at f/22 you had only 2mp worth of resolution (a statement he applied to both the 1dsII and the 5d--see his original post).
so here's the problem: myhrvold actually was completely consistent (and equally wrong) in both of his posts. this makes it harder to believe that the way he got there was through misplacing decimals on the radius calculation, or confusing radius and diameter (though perhaps that was a factor).
i still suspect, as i stated in my first post, that the problem is related to misunderstanding how the interpolated data from multiple photosites relates to 'pixels'. that would be an interesting subject to take up, in my opinion. it would be helpful to know how interpollation affects the diffraction limits (and i am unconvinced by myhrvold's dismissal of it given my tests). i could read the papers johnson references; i bet they would help. but it just isn't that high on my list of things to do. in the meantime i will continue to get results from my camera at f/16-22 which, according to myrhvold, violate the laws of physics.