(single-coated)

OM-1 with mirror lockup
Vignetting = A
Distortion = none
Aperture Center Corner
f/2.8    D-     D-
f/4      C      C
f/5.6    B-     B-
f/8      B      B
f/11     B      B
f/16     B+     B+
f/22     B+     B+

OM-4T with mirror and aperture prefire;
same lens as OM-1 based test
Aperture Center Corner
f/2.8    B-     B-
f/4      B      B
f/5.6    A-     B+
f/8      B      B
f/11     B      B
f/16     C+     C+
Very low contrast at f/22; moderately low contrast at f/16; moderate contrast at f/4, f/5.6 and f/11; moderately high contrast at f/8.

100mm f/2.8 Zuiko (single-coated) with Olympus 2X Teleconverter
OM-1 with mirror lockup
Vignetting = B+
Distortion = slight pincushion
Aperture    Center Corner
f/2.8 (5.6) F+     D-
f/4 (8)     D      D
f/5.6 (11)  C-     C
f/8 (16)    B      B-
f/11 (22)   B+     B
f/16 (32)   B      B-
f/22 (44)   B-     B-
Notes: Moderately low contrast at small apertures.