Canon FD 24mm f/2 bayonet mount
Canon EF with mirror and aperture prefire

Vignetting = C @ f/2, B @ f/2.8, A- @ f/4, A thereafter
Distortion = slight waveforming with slight barrel tendency

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

Notes:
* = tested with a Promaster 1A filter.
Moderate contrast images at f/2 (with and without filter)
through f/4; moderately high contrast images at f/5.6 through f/22.