Vivitar Series 1 70-210mm f/2.8~4.0 (multi-coated)
OM-1 WITHOUT mirror lockup

@ 70mm setting
Vignetting = B-
Distortion = slight barrel
Aperture Center Corner
f/2.8    B      B-
f/4      B      B
f/5.6    B+     B+
f/8      B      A-
f/11     B-     B
f/16     B-     B-
f/22     B-     B-
Notes: High contrast images; remarkably even performance at 70mm through the aperture range; difficult to determine effective aperture when shooting wide open (click stops somewhat confusing); performance loss wide open at 210mm characteristic of telephoto lens without ED type glass.

@ 140mm setting
Vignetting = A-
Distortion = slight pincushion
Aperture  Center Corner
f/2.8~4.0 B      C
f/4       B+     B-
f/5.6     A-     B
f/8       B+     B
f/11      B      B
f/16      B      B
f/22      B-     B-

@ 210mm setting
Vignetting = B+
Distortion = pincushion
Aperture Center Corner
f/4      C+     C-
f/5.6    B-     C+
f/8      B-     B-
f/11     B-     C
f/16     B      B-
f/22     B-     C