(multi-coated)

OM-4T with mirror and diaphragm prefire

Distortion: waveform
Aperture Center Corner Vignetting Contrast
f/2      B+     C      D          mod. high
f/2.8    B+     C+     C          mod. high
f/4      A-     B+     B          very high
f/5.6    A-     A-     B          extra high
f/8      A      B+     A-         very high
f/11     A-     B+     A-         very high
f/16     A-     B+     A-         very high