(multi-coated)

OM-1 with mirror lockup, sample 1 (Zuiko)

Vignetting = B+ @ f/2
Distortion = slight pincushion

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

Notes: Moderate contrast.

OM-4T with mirror and diaphragm prefire, sample 2 (Zuiko MC)

Vignetting = B+ @ f/2, A- @ f/2.8, A thereafter
Distortion = none

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

Notes: Moderate contrast at f/11-16, moderately high contrast at f/4-8, high contrast at f/2-2.8. Remarkable performance at f/2.8 in this sample.