Mamiya 55mm 2.8 C-N sharpest setting?

Most lenses perform better at certain apertures, usually stopped down a couple of stops from its widest aperture. Does anyone know about the Mamiya 55mm 2.8 C N for 645? Which aperture would yield the best results for this particular lens? I have read somewhere info about 35mm lenses in which tests were performed to determine their prime settings. Is there anything similar out there for Mamiya lenses (for 645 manual focus and for their RB and RZ series)?

A good question. One that I too hope will be answered in this thread. I have this lens and have used it stopped down completely for some table top product photography and mine is quite sharp at that setting. But I have also heard that most lenses will be sharpest around f-8. I would love to know whether this is fact or legend.

Usually the mid point of the aperture scale for any lens. So if you lens is a 2.8 and stops down to 22, f/8.0 will yield the 'sharpest' results.

You results may vary. I suggest you do a test with the camera on a tripod.

It is sharpest wide open, but you'll have quite a thin DoF. Contrast improves stopped down, and you'll get the most accutance at f/5.6-f/8. but for pretty much any lens, the raw resolution is always highest wide open.