Hoya 75-260mm f/4.5
OM-1 with mirror lockup

@75mm setting
Vignetting = B
Distortion = slight barrel
Aperture Center Corner
f/4.5    B-     B-
f/5.6    B+     B+
f/8      B+     B+
f/11     A-     B+
f/16     B+     B
f/22     B-     B-
Notes: Moderate contrast.

@ 135mm setting
Vignetting = C+ @ f/4.5, B+ @ f/5.6, A- @ f/8
Distortion = moderate pincushion
Aperture Center Corner
f/4.5    C+     C+
f/5.6    B      B
f/8      A+     A-
f/11     A      B
f/16     B+     B
f/22     B      B-
Notes: Moderate contrast @ f/4.5 & f/22, high contrast @ f/8 & f/11.

@ 260mm setting
Vignetting = C- @ f/4.5, B @ f/5.6, A- @ f/8
Distortion = pronounced pincushion
Aperture Center Corner
f/4.5    C      C+
f/5.6    B-     B-
f/8      B      B-
f/11     A-     B-
f/16     B+     B
f/22     B      C+
Notes: Moderately high contrast.