(multi-coated)

@ 85mm setting
OM-1 with mirror lockup, sample 1
Vignetting = B- @ f/5, A @ f/8
Distortion = very slight barrel
Aperture Center Corner
f/5      B      B+
f/8      B      B+
f/11     B      B+
f/16     B+     B
f/22     B      B
f/32     *      *
Notes: Moderately high contrast. * = no data.

OM-4T with mirror and diaphragm prefire, sample 2
Vignetting = A- @ f/5, A thereafter
Distortion = slight barrel
Aperture Center Corner
f/5      B      B+
f/8      B+     A
f/11     A-     A
f/16     B+     A-
f/22     B+     B+
f/32     B      B
Notes: Moderate contrast at f/22-32, moderately high contrast at f/5-8 and f/16, high contrast at f/11. Remarkably easy to focus at all focal lengths with a 2-4 screen.

@ 135mm setting
OM-1 with mirror lockup, sample 1
Vignetting = B- @ f/5
Distortion = none
Aperture Center Corner
f/5      B      B
f/8      B+     B+
f/11     A-     A-
f/16     B+     B+
f/22     B+     B
f/32     *      *
Notes: High contrast. * = no data.

@ 150mm setting
OM-4T with mirror and diaphragm prefire, sample 2
Vignetting = A- @ f/5, A thereafter
Distortion = slight pincushion
Aperture Center Corner
f/5      B+     A-
f/8      B      B+
f/11     B+     A-
f/16     B+     B+
f/22     B      B
f/32     B      B-
Notes: Moderate contrast at all apertures. Exceptional ease of focus with a 2-4 screen.

@ 180mm setting
OM-1 with mirror lockup, sample 1
Vignetting = B
Distortion = moderate pincushion
Aperture Center Corner
f/5      B-     B-
f/8      B      B
f/11     B      B
f/16     B      B
f/22     B      B
f/32     B-     B-
Notes: Moderately high contrast at f/11 to f/32, moderate at f/5 to f/8.

@ 250mm setting

OM-1 with mirror lockup, sample 1
Vignetting = B @ f/5
Distortion = pronounced pincushion
Aperture Center Corner
f/5      B-     B-
f/8      B      B
f/11     B      B
f/16     B      B
f/22     A-     B+
f/32     B+     B+
Notes: Moderately high contrast. Well balanced and very stable when used with the tripod collar.

OM-4T with mirror and diaphragm prefire, sample 2
Vignetting = B- @ f/5 with filter, A- @ f/5 without, A- @ f/8,A thereafter
Distortion = moderate pincushion
Aperture Center Corner
f/5*     C+     C+
f/5      B      B-
f/8      B-     B-
f/11     B      B
f/16     B      B-
f/22     **     **
f/32     **     **
Notes: * = with Hoya Skylight filter, which exhibits moderate contrast images. Moderate contrast at f/16, moderately high at f/5-11. ** = no SQF or contrast data available at f/22-32.