Benny:
A well focussed and well exposed negative or slide taken with either a 45mm or 55mm Mamiya N lens for the 645 series cameras that is in reasonable condition will be exhibit way more "sharpness" (resolution, contrast and accutance) than one will be able to evaluate by comparing web postings in a thread or 4x6 prints.
The problem with using small prints or web postings to evaluate lenses is that it is impossible to see fine differences, and that the quality of the process (scanning, posting or printing) will have more affect than the lenses themselves.
FWIW, this attachment was shot using a 55mm lens. The scan was done from an 8x10 optical print.
EDIT: As I re-read my posts in this thread, it seems to me that I am coming across as, well, kind of grumpy!
That's not what I intended, so I apologize for that.
What I would like to indicate instead, is that any discussion about the relative "sharpness" of any modern medium format lens manufactured by any of the major manufacturers (Mamiya, Hasselblad, Rollei, Pentax, etc.) is a discussion about fine differences out at the edges of performance requirements.
The differences are real, but they are small, and as much differences of character and prioritization as anything else.
To give a sense of perspective, the differences between lenses are much less apparent than the difference in the results obtained when comparing hand-held and tripod mounted shots.
As I understand it, BennyK is trying to decide on a camera purchase. A Mamiya 645E with a 45mm N lens is a very capable package. The photographs one can take with it will be different than those created with a 55mm lens on the same body, but the difference in angle of view will be far greater than differences in quality.
From my point of reference, the differences in the filter size and barrel thickness between the two lenses are of more importance than the very small differences between the excellent image quality that they are capable of.
And if you are wondering, the reason that barrel thickness matters to me is that the slightly thicker 45mm lens won't work with the focus assist lever that my other 3 lenses work with, and that is inconvenient (to me).
To add just a bit more perspective, I'm attaching another image - the one with the fallen tree. It was shot with a 35mm scale focussing camera - an Olympus Trip 35 with a capable lens that I paid $2.10 for. I am adding it to show how hard it is to show fine differences between lenses using web examples.
