Olympus 250mm f/2 Zuiko (multi-coated)

(multi-coated)

Vignetting = C @ f/2, A- @ f/2.8, A @ f/5.6
Distortion = none

OM-4 w/ mirror and aperture prefire
Aperture Center Corner
f/2      A      B+
f/2.8    A+     A-
f/4      A+     A
f/5.6    A+     A+
f/8      A      A-
f/11     A-     A-
f/16     A-     A-
f/22     A-     B+
Notes: Extremely high contrast and resolving power at all apertures with only a minor loss in the corners at f/2 and f/22. Strong vignetting at f/2, requiring exposure compensation for critical work. Probably the best overall image quality of any OM System Zuiko lens made. Brillant images with f/5.6 showing corner to corner clarity unsurpassed by any Zuiko tested.

OM-1n with mirror lock-up
Aperture Center Corner
f/2      D      C
f/2.8    D+     C
f/4      C      C+
f/5.6    B-     B-
f/8      B-     B-
f/11     B+     B
f/16     C+     C
f/22     B-     B
Notes: Combination of vibrations from the auto diaphram mechanism and the horizontally traveling shutter of the OM-1n results in significant image deterioration, despite secure tripod mounting of the lens bracket. Note that differences between this test and the one above with the OM-4 are significant at the 1/3 grade level based on side by side comparisons. Test conditions were identical and I used the same lens.

250mm f/2 Zuiko with Olympus 1.4x teleconverter (both multi-coated)
OM-4 w/ mirror and aperture prefire
Vignetting = C+ @ f/2, A- @ f/2.8
Distortion = moderate pincushion
Aperture  Center Corner
f/2 (2.8) A-     B
f/2.8 (4) A      B+
f/4 (5.6) A      A-
f/5.6 (8) A      A-
f/8 (11)  B+     B
f/11 (16) B+     B
f/16 (22) B+     B-
f/22 (32) B-     C+
Notes: Moderate to moderately high contrast. Exceptional wide open performance.

250mm f/2 Zuiko with Olympus 2X teleconverter (both multi-coated)
OM-4T with mirror and aperture prefire and additional monopod support on camera
Vignetting = B- @f/2.8 (5.6), A- @f/4 (8) and f/5.6 (11), A thereafter
Distortion = very slight waveforming with no tendency
Aperture*   Center Corner
f/2.8 (5.6) C+     C-
f/4 (8)     C+     C
f/5.6 (11)  C+     C
f/8 (16)    C+     C
f/11(22)    B-     B-
f/16 (32)   B-     B-
f/22 (44)   B      B
f/32 (64)   C      C-
Notes: *Effective aperture in parenthesis (). Not an Olympus recommended combination. Moderately high contrast images atf/2.8 (5.6),f/4 (8), then f/11 (22) throughf/32 (64); high contrast images at f/5.6 (11) & f/8 (16).