Canon FD 100mm f/2 (bayonet mount)
Canon EF w/ mirror and diaphragm prefire

Vignetting: B @ f/2, A- @ f/2.8, A thereafter
Distortion: slight pincushion

Aperture Center Corner
f/2      B-     B+
f/2.8    A-     A-
f/4      A      A
f/5.6    A      A
f/8      A-     A-
f/11     A      A
f/16     B+     B+
f/22     B+     B+
f/32     B      B

Notes:
moderate contrast at f/2 and f/32;
moderately high contrast at f/2.8, f/4, f/16 and f/22;
high contrast at f/5.6; very high contrast at f/8 and f/11.