(multi-coated)

OM-4T with mirror and diaphragm prefire

Vignetting = C @ f/1.2, B @ f/1.5, B+ @ f/2, A @ f/2.8
Distortion = slight barrel (none?)

Aperture  Center    Corner   Contrast
f/1.2     C         C+       Mod. high
~f/1.5    B-        C+       High
f/2       B-        B-       High
f/2.8     A-        A-       High
f/4       A-        A-       High
f/5.6     B+        A-       High
f/8       A-        A-       High
f/11      B+        A-       High
f/16      B+        B        High

Notes: Average of three different samples (except contrast grades from one sample).