(single-coated)

50mm f/1.8 Zuiko (single-coated)

OM-1 with mirror lockup

Vignetting = B
Distortion = slight barrel

Aperture Center Corner
f/1.8    D+     B-
f/2.8    C+     B-
f/4      B      B
f/5.6    B      B
f/8      B      B+
f/11     B+     A-
f/16     B+     A-

Notes: Slightly soft contrast.

50mm f/1.8 Zuiko (single-coated)
OM-4T with mirror and aperture prefire

Vignetting = B @ f/1.8, A @ f/2.8 and thereafter
Distortion = slight barrel

Aperture Center Corner
f/1.8    B      B-
f/2.8    B+     B
f/4      B+     B+
f/5.6    B      B+
f/8      A-     A-
f/11     B+     B+
f/16     B      B

Notes: Moderate contrast at all apertures.