(single-coated)

data for two examples (7 condition,9 condition);

OM-1 with mirror lockup

Vignetting = A
Distortion = none

Aperture Center Corner
f/2      D,D    C,C-
f/2.8    B,C+   B,C+
f/4      B,B-   B-,B-
f/5.6    B,B    B-,B+
f/8      B+,A-  A-,A
f/11     A-,A-  B+,B+
f/16     A-,B+  A-,B+

Notes: 7 condition lens with coating loss due to fungus removal treatment, shows moderate contrast images; 9 condition lens shows contrasty image. Fine detail evident in both lenses stopped down. SQF grade differences are insignificant between lenses at all apertures.

OM-4T with mirror and aperture prefire; same 7 condition lens as above, early 6 element version

Aperture Center Corner
f/2      C      C
f/2.8    B+     B
f/4      B+     B+
f/5.6    B+     B+
f/8      B+     B
f/11     B      B
f/16     B-     B-

Notes: Low contrast images at f/2; moderately low contrast at f/2.8, f/11 and f/16; moderate contrast at f/4 to f/8.