Vivitar Series 1 35-85mm f/2.8 (multi-coated)
OM-2000 with mirror and aperture prefire

@ 35mm setting
Vignetting = B- @ f/2.8, B+ @ f/4, A- @ f/5.6
Distortion = slight waveform with moderate barrel tendency
Aperture Center Corner
f/2.8    C      C
f/4      A-     C+
f/5.6    A      B+
f/8      A-     A-
f/11     B+     B+
f/16     B+     B
Notes: Moderately high contrast.

@ 60mm setting
Vignetting = B- @ f/2.8, B+ @ f/4, A- @ f/5.6
Distortion = slight waveform with pincushion tendency
Aperture Center Corner
f/2.8    C      C+
f/4      B      B
f/5.6    A-     B+
f/8      A-     A-
f/11     B+     B
f/16     B      B
Notes: Moderately high contrast.

@ 85mm setting
Vignetting = B- @ f/2.8, B+ @ f/4, A- @ f/5.6
Distortion = strong pincushion
Aperture Center Corner
f/2.8    C+     C
f/4      B-     C+
f/5.6    B+     B
f/8      A-     A-
f/11     A-     A-
f/16     A-     B+
Notes: Moderately high contrast.