Tokina RMC 28-85mm f/4 (multi-coated)
OM-4T with mirror and diaphragm prefire

@ 28mm setting
Vignetting = B @ f/4, B+ thereafter
Distortion = slight waveforming with moderate pincushion tendency
Aperture Center Corner
f/4      A-     B+
f/4*     B+     B
f/5.6    A      B+
f/8      A-     B+
f/11     A      B
f/16     B+     B+
Notes: * = with Hoya 1B filter. High contrast images in center and moderately high contrast in corners at f/4 (with and without filter) to f/5.6; very high contrast images in center and moderately high contrast in corners at f/8 to f/11; very high contrast images in center and high contrast in corners at f/16.

@ 35mm setting
Vignetting = A- @ f/4, A thereafter
Distortion = slight waveforming with
moderate barrel tendency
Aperture Center Corner
f/4.0    B      B
f/5.6    A-     B+
f/8      A      B+
f/11     A      A-
f/16     A-     A-
Notes: high contrast images in center and moderately high in corners at f/4; very high contrast images in center and high contrast in corners at f/5.6 to f/16.

@ 50mm setting
Vignetting = A- throughout
Distortion = none
Aperture Center Corner
f/4.0    B+     B+
f/5.6    B      B
f/8      B      B+
f/11     B+     A-
f/16     B+     B+
Notes: high contrast images in center and moderate contrast in corners at f/4; very high contrast images in center and high contrast in corners at f/5.6 to f/8; high contrast images in center and moderately high contrast in corners at f/11 to f/16.

@ 85mm setting
Vignetting = B @ f/4, A- @ f/5.6, A thereafter
Distortion = moderate pincushion
Aperture Center Corner
f/4.0    B-     B-
f/5.6    B+     B
f/8      A-     B
f/11     B+     B
f/16     B+     C+
Notes: high contrast images in center and corner at f/4; very high contrast in center and high contrast in corners at f/5.6 and f/8; moderately high contrast in center and corners at f/11; moderately high contrast in center and moderate in corners at f/16.