(multi-coated)

@ 28mm setting

OM-1 with mirror lockup
Vignetting = B- @ f/4, B+ @ f/5.6
Distortion = waveform with distinct barrel tendency
Aperture Center Corner
f/4      B      C
f/5.6    B      B-
f/8      B+     B
f/11     B+     B
f/16     B+     B
f/22     B     B
Notes: Moderate contrast, except at f/22 which was low.

OM-2S with mirror and diaphragm prefire, different lens sample (serial number 1153xx) vs. OM-1 test
Vignetting = A- @ f/4, A thereafter
Distortion = slight waveform with no tendency
Aperture Center Corner
f/4      B      C
f/5.6    A-     B
f/8      A-     A
f/11     A-     A-
f/16     B+     B+
f/22     B+     B+
Notes: Moderate contrast images at f/4 to f/5.6 and f/16 to f/22; moderately high contrast images at f/8 to f/11.

@ 35mm setting

OM-1 with mirror lockup
Vignetting = B at f/4
Distortion = moderate barrel
Aperture Center Corner
f/4      C+     C-
f/5.6    B-     B-
f/8      B      B
f/11     B      B
f/16     B      B
f/22     B-     B-
Notes: Moderate contrast images, except at f/4 and f/22 which was low.

OM-2S with mirror and diaphragm prefire, different lens sample (serial number 1153xx) vs. OM-1 test
Vignetting = B+ at f/4, A thereafter
Distortion = slight waveform with barrel tendency
Aperture Center Corner
f/4      B      C-
f/5.6    A-     B-
f/8      B+     B
f/11     B+     B+
f/16     B+     B
f/22     B+     B
Notes: Moderate contrast images in center and low in corner at f/4; moderately high contrast images in center and moderate in corners at f/16 to f/22; moderate contrast images at f/5.6 to f/8; moderately high contrast images a f/11.

@ 48mm setting

OM-1 with mirror lockup
Vignetting = B- @ f/4
Distortion = none
Aperture Center Corner
f/4      B      C
f/5.6    B      C+
f/8      B      B-
f/11     B+     B-
f/16     B      B-
f/22     B-     B-
Notes: Moderate contrast images, except at f/22 which was moderately low.

OM-2S with mirror and diaphragm prefire, different lens sample (serial number 1153xx) vs. OM-1 test
Vignetting = B @ f/4, B+ @ f/5.6, A- @ f/8, A thereafter
Distortion = slight waveforming with pronounced barrel tendency
Aperture Center Corner
f/4      A-     C
f/5.6    A-     B
f/8      B+     B+
f/11     B+     B+
f/16     B+     B+
f/22     B      B
Notes: Moderate contrast images in center and low in corners at f/4; moderate contrast images at f/5.6 and f/11 through f/22; moderately high contrast images at f/8.