Just to give you a reference, below I tested the Pentax Macro 50mm f4 on my Pentax body using Kodak Techpan @ ISO25, ideal shooting condition and setup with a 12233 resolution test chart to provide the detail need to evaluate the overall resolving power of this system.
Full res version ->
http://www.fototime.com/8372250EA44CB06/orig.jpg
I did this test on my lenses as I wasn't sure just how good - or bad, they are given that they were not factory new. As you can see from the results above, not even a 36MP Nikon D800 can resolve all the detail this lens can resolve. As a result of this test, I can't determine what is the limiting factor - is it the lens or the film or some other?
I've tested all my Pentax prime lenses - bought used, and they will not be the limiting factor in achieving all the detail that the scene has.