Canon FD 24mm f/2.8 bayonet mount 
Canon EF with mirror and diaphragm prefire

Vignetting = B- @ f/2.8, B+ @ f/4, A thereafter
Distortion = barrel

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

Notes:
moderately low contrast at f/2.8;
moderately high contrast at f/4;
high contrast at f/5.6 to f/22.