(multi-coated) OM-2000 with mirror and aperture prefire Vignetting = C+ @ f/2, B at f/2.8, B @ f/4, A- thereafter Distortion = none Aperture Center Corner f/2 B+ A- f/2.8 A- B+ f/4 B+ B f/5.6 A- B+ f/8 A- A- f/11 A- B+ f/16 A- B- f/22 A- B- Notes: Moderately high contrast images at f/22; high contrast images at f/2, f/2.8 and f/16; very high contrast images at f/4, f/5.6 and f/11; extremely high contrast images at f/8. Paired SQF grade and contrast comparisons to the Leitz 90mm f/2 Summicron-R testdone on a Leicaflex, with SQF differences significant at the 1/3 grade level. Condition: 9+ (KEH=Ex+).
OM-1 with mirror lockup; condition: 10- Aperture Center Corner f/2 C B- f/2.8 B- B- f/4 B+ B f/5.6 A- B f/8 A A- f/11 A A- f/16 A- B+ f/22 B B- Notes: Design favors center sharpness; clearly diffraction limited at f/22
90mm f/2 Zuiko Macro (multi-coated) with 1.7x teleconverter for IS/3 OM-4T with mirror and diaphragm prefire Distortion: pronounced pincushion Aperture* Center Corner Vignetting Contrast f/2 B- C- B moderate f/2.8 B C- B moderate f/4 B C+ A- mod. high f/5.6 B B- A- moderate f/8 B B- A- moderate f/11 B B A- mod. low f/16 B B A- mod. low f/22 B B- A- mod. low Notes: *aperture on primary lens.
90mm f/2.0 Zuiko Macro (multi-coated) with Olympus 2X Teleconverter OM-1 with mirror lockup Vignetting = B+ Distortion = slight pincushion Aperture Center Corner f/2 (4) F F f/2.8 (5.6) F+ C+ f/4 (8) C- C- f/5.6 (11) C C- f/8 (16) C+ C f/11 (22) B- C f/16 (32) C+ C f/22 (45) C+ D+ Notes: A non-recommended combination which requires modification of the 90mm lens to mount a 2X Teleconverter. Unacceptably low contrast at f/2, exceedingly low contrast at f/5.6, low contrast at f/8.