Canon FD 135mm f/3.5 Pre-S.C. breech
Canon F-1 w/ mirror and diaphragm prefire

Vignetting: A- @ f/3.5, A thereafter
Distortion: slight pincushion

Aperture Center Corner
f/3.5    B      B-
f/5.6    B+     B
f/8      A-     B
f/11     B+     B
f/16     B      B
f/22     B      B

Notes:
moderately low contrast at f/3.5 and f/22;
moderate contrast at f/5.6, f/11 and f/16;
moderately high contrast at f/8.

same camera and lens sample as above, with a generic brand UV filter

Aperture Center Corner
f/3.5    C+     C+

same camera and lens sample as above, with a Canon brand UV filter

Aperture Center Corner
f/3.5    B-     B-