Canon FD 50mm f/1.4 breech mount (S.S.C.)
Canon EF with mirror and diaphragm prefire

Vignetting = C+ @ f/1.4, B+ @ f/2, A- @ f/2.8, A thereafter
Distortion = barrel

Aperture Center Corner
f/1.4    B-     C
f/2      B+     B-
f/2.8    A-     A-
f/4      A-     A-
f/5.6    B+     B+
f/8      B+     B+
f/11     B+     B
f/16     B      B

Notes:
moderately low contrast at f/1.4;
moderate contrast at f/2;
moderately high contrast at f/2.8;
high contrast at f/4 and f/5.6;
very high contrast at f/8 through f/16.