The Nikon D7100 happens to have a sensor pixel density that makes it equivalent in resolution requirements to a 56-megapixel full-frame DSLR. It also lacks an anti-aliasing filter and thus allows peak lens performance to be recorded without any artificial blurring of detail.
Naturally I’d like to know: when that 56-megapixel (or similar) Nikon D4x arrives, perhaps later this year, just how will the Zeiss 135mm f/2 APO-Sonnar perform?
Now in Guide to Zeiss is perhaps the most interesting study of diffraction and MTF that I’ve yet published: Zeiss 135mm f/2 APO-Sonnar on 56-Megapixel (equiv) DSLR.
Included are several generously-sized crops from f/2 through f/22 along with MTF charts from f/2 through f/22 as measured from an actual production lens. Hence one can directly relate the MTF charts to the actual performance as seen in real life—for every aperture.
It’s only a matter of time before we actually have a full-frame 56-megapixel DSLR (or 50 or 70 or whatever it actually happens to be). This carefully made and definitive study is thus not abstract at all, but directly relevant to the near future.
Also published in Making Sharp Images is a condensed version of the same study (fewer crops, but just as instructive). Also the San Francisco series with the Canon 1Ds Mark III has been redone with more and larger crops.