(multi-coated)

OM-4 with mirror and diaphragm prefire, used on a 25mm auto extension tube

Vignetting = B @ f/4, A- @ f/5.6, A thereafter
Distortion = slight pincushion

Aperture Center Corner
f/4      C+     C
f/5.6    B+     B-
f/8      A-     B
f/11     A-     B
f/16     A-     B
f/22     B      B-
f/32     B-     B-

Notes: Moderate contrast, except low at f/32. Optimum apertures f/8-f/16. Since this lens is optimized for 2:1 to 1:2 reproduction ratios, these test results at 1:40 are for experimental purposes only.