Less of a difference than the film format apparently, as per the information given in the link mentioned above. I guess I was a spouting a half truth, the resolution afforded by say a 4x5 format would make the diffraction from a small aperture like f45 basically negligible. However the same focal length/stop used on 35mm would suffer from ill effects of diffraction due to the smaller circle of confusion vs. the diameter of the airy disk. Play with the calculator it's interesting stuff.
Originally Posted by BradS