(single-coated, shift-lens)

OM-1 with mirror lockup, first lens sample

@ no offset
Vignetting = A- @ f/2.8
Distortion = barrel
Aperture Center Corner
f/2.8    C-     C-
f/4      C+     B-
f/5.6    B      B
f/8      B+     A-
f/11     B+     A
f/16     B+     B
f/22     B-     B

@ maximum vertical offset
Vignetting = B- in furthest corners @ f/2.8
Distortion = barrel
Aperture Center Corner
f/2.8    D      C
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-

OM-2S with mirror and diaphragm* prefire, 2nd lens sample

@ no offset
Vignetting = B @ f/2.8, A- @ f/4, A thereafter
Distortion = slight barrel (none?)
Aperture Center Corner
f/2.8    B-     C
f/4      A-     B+
f/5.6    A-     A
f/8      B+     A-
f/11     B+     B+
f/16     B      B
f/22     B-     B-
Notes: Moderate contrast in center and moderately low contrast in corners at f/2.8 and f/16; moderate contrast at f/4; moderately high contrast in center and moderate in corners at f/5.6, f/8 and f/11; moderate contrast in center and moderately low contrast in corners at f/16. This lens lacks an automatic diaphragm, so the use of the self timer to attain "mirror and diaphragm prefire" maybe less important than with other lenses.

@ maximum offset
Vignetting = C (upper), B (lower) @ f/2.8; B,A @ f/4; A-,A @ f/5.6 & f/8; A,A thereafter
Distortion = none
Aperture Center Corner
f/2.8    C      C
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 at f/2.8, moderately high contrast in center and moderate contrast in corners at f/4 and f/5.6, moderately high contrast in center and corners at f/8 and f/11, high contrast in center and moderately high contrast in corners at f/16, moderate contrast in center and moderately low contrast in corners at f/22.