Tamron SP 350mm f/5.6 (catadioptric lens)

OM-1 with mirror lockup
Vignetting = C
Distortion = pronounced barrel
Aperture Center Corner
f/5.6    B+     B+
Notes: Moderate contrast images.

OM-4T with mirror and diaphragm prefire, different sample from
above OM-1 test
Vignetting = B
Distortion = pronounced pincushion
Aperture Center Corner
f/5.6    B+     B
Notes: High contrast images.

Tamron SP 350mm f/5.6 (catadioptric lens) with Tamron SP 2X Teleconverter
OM-4T with mirror and diaphragm prefire, different sample from above OM-1 test
Vignetting = A- to B+
Distortion = pronounced pincushion
Aperture*  Center Corner
f/5.6 (11) C      C
Notes: *Effective aperture in parenthesis (). Moderately high contrast in center and moderate contrast images in corners.