(multi-coated) OM-4T with mirror and diaphragm prefire (sample 1) Vignetting = B+ @ f/2, A- @ f/2.8 Distortion = slight pincushion Aperture Center Corner f/2 A A- f/2.8 B+ B f/4 B+ B+ f/5.6 A- A- f/8 B+ B+ f/11 B+ B f/16 A- B+ f/22 A B+ Notes: Extremely high contrast at f/2 and f/22; high contrast at f/2.8 to f/16. OM-4T with mirror and diaphragm prefire (sample 2) Distortion: slight pincushion Aperture Center Corner Vignetting Contrast f/2 B+ B B- mod. high f/2.8 A- B+ A? mod. high f/4 A- A- B+ high f/5.6 A A+ A- very high f/8 A A A- high f/11 A+ A- A extr. high f/16 A- A A very high f/22 A B+ A very high 180mm f/2.0 Zuiko (multi-coated) with Olympus 1.4X Teleconverter OM-4T with mirror and aperture prefire (sample 1) Vignetting = B+ @f/2 (2.8), A- @f/2.8 (4) Distortion = none Aperture Center Corner f/2 (2.8) D B- f/2.8 (4) A- B f/4 (5.6) B+ B+ f/5.6 (8) B- B f/8 (11) A- B+ f/11 (16) A- A- f/16 (22) A- B f/22 (32) B+ B Notes: Moderately low contrast atf/2 (effective f/2.8); very high contrast at f/8 and f/11; high contrast at f/16. OM-4T with mirror and diaphragm prefire (sample 2) Distortion: slight pincushion Aperture Center Corner Vignetting Contrast f/2 (2.8) C B+ A- high f/2.8 (4) A+ A- A v. high f/4 (5.6) A+ A- A v. high f/5.6 (8) A- B+ A high f/8 (11) A B+ A high f/11 (16) A A A v. high f/16 (22) A A- A v. high f/22 (32) A A- A v. high 180mm f/2 Zuiko (multi-coated) with Olympus 2x teleconverter OM-4T with mirror and diaphragm prefire Distortion: pincushion Aperture Center Corner Vignetting Contrast f/2 (4) C C B v. low f/2.8 (5.6) B+ C+ A high f/4 (8) A- B A v. high f/5.6 (11) B- C+ A moderate f/8 (16) B B- A mod. low f/11 (22) B B- A mod. low f/16 (32) B- B- A mod. low f/45 C+ C+ A moderate