Tokina AT-X 90mm f/2.5 Macro
OM-1 with mirror lockup
Vignetting = B @ F/2.5, A- @ f/4
Distortion = None
Aperture Center Corner
f/2.5    B-     C
f/4      B      C+
f/5.6    C      B-
f/8      C+     B-
f/11     B      B-
f/16     B+     B+
f/22     B+     B+
f/32     B-     B
Notes: Moderate contrast with lack of resolution.