(multi-coated, serial number under 500,000)

@ 35mm setting
OM-4 with mirror and diaphragm prefire
Vignetting = C+ @ f/3.5, B+ @ f/5.6 & f/8, A thereafter
Distortion = slight barrel
Aperture Center Corner
f/3.5    B+     C
f/5.6    A-     B-
f/8      B+     B+
f/11     A-     A-
f/16     B+     B+
f/22     B      B
Notes: Moderate contrast at f/3.5, f/16 & f/22; moderately high at f/5.6; high at f/8 & f/11.

@ 50mm setting
OM-1 with mirror lockup
Vignetting = B- @ f/4
Distortion = pincushion
Aperture Center Corner
f/4      B-     B
f/5.6    B      B
f/8      B+     A-
f/11     B+     A-
f/16     A-     A-
f/22     A-     A-

@ 70mm setting
OM-4 with mirror and diaphragm prefire
Vignetting = B @ f/4, A- @ f/5.6, A thereafter
Distortion = pincushion
Aperture Center Corner
f/4.0    C      C+
f/5.6    A-     B+
f/8      A      A
f/11     B+     B+
f/16     B      B+
f/22     B-     B-
Notes: Moderately high contrast lens, except moderately low at f/4.

@ 105mm setting
OM-1 with mirror lockup
Vignetting = B+
Distortion = none
Aperture Center Corner
f/4.5    B-     B-
f/5.6    B      B
f/8      B+     B+
f/11     B      B
f/16     B      B+
f/22     B      B+
Notes: Very contrasty, but length of lens on an OM-1 results in lower SQF grades due to vibration.

OM-2000 with mirror and aperture prefire
Aperture Center Corner
f/4.5    A-     B
f/5.6    B+     B
f/8      A-     B+
f/11     A-     B+
f/16     A-     B
f/22     B      B-
Notes: Very high contrast at the expense of resolution.