(multi-coated)

@ 35mm setting
OM-1 with mirror lockup
Vignetting = B @ f/2.8, B+ @ f/4, A @ f/5.6
Distortion = pronounced barrel
Aperture Center Corner Popular Photography
f/2.8    B+     B      B+
f/4      A-     B      B+
f/5.6    A-     B+     B+
f/8      A      A-     B+
f/11     A      B+     B+
f/16     A-     B      B
f/22     A-     B      C+
Notes: High contrast at f/8, moderately high contrast elsewise. Popular Photography SQF grades from August 1995 issue; averaged for the entire field of view, at 22X magnification.

@ 50mm setting
OM-1 with mirror lockup
Vignetting = B- @ f/2.8
Distortion = very slight pincushion
Aperture Center Corner Popular Photography
f/2.8    C+     C+     B
f/4      B      B      B+
f/5.6    A-     A-     A
f/8      A      A      A
f/11     A      A      B+
f/16     B+     A-     B
f/22     B+     B      C+
Notes: Moderately low contrast.

@ 80mm setting
OM-1 with mirror lockup
Vignetting = B @ f/2.8,B+ @ f/4
Distortion = moderate pincushion
Aperture Center Corner Popular Photography
f/2.8    B-     C+     C+
f/4      B-     B-     B
f/5.6    B+     B      A
f/8      A-     B      A
f/11     A      B      A
f/16     A-     B      B+
f/22     B+     B      B
Notes: Exceptionally high contrast at f/8, high contrast elsewise.

OM-4 with mirror and auto diaphram prefire, plus Bogen Telephoto Lens Support
Aperture Center Corner
f/2.8    B+     B-
f/4      A-     B+
f/5.6    A      A-
f/8      A      A-
f/11     A      B
f/16     A-     B
f/22     B+     B
Notes: Differences between OM-1 with mirror lockup and this OM-4 test are significant at the 1/3 grade level since they were determined from paired comparisons. The greatest differences are at shutter speeds of 1/30th (f/8), 1/60th (f/5.6), 1/125th (f/4), and 1/250th (f/2.8), indicating that 1) shutter vibrations from the horizontal shutter in the OM-1 and 2) automatic aperture mechanism movements significantly degrade even a lens in the short telephoto range.