Nikon Micro-Nikkor 55mm f/2.8 AIS (multicoated)
Nikon F2 with mirror and diaphragm prefire

Distortion: slight waveform with no tendencies
Vignetting: A- @ f/2.8, A thereafter

Aperture Center Corner
f/2.8    A-     B+
f/4      A      A-
f/5.6    A      A-
f/8      A+     A+
f/11     A      A-
f/16     B+     A-
f/22     B      B
f/32     B-     B-

Notes: High contrast at f/2.8 and f/16; very high contrast at f/8 and f/11; extremely high contrast at f/5.6; moderately high contrast (diffraction limited) at f/22 and f/32. Remarkable image detail at f/8 - the optimal aperture.