Folks:
This lens is so exceptional I had to post the results right to the list. I
couldn't believe my eyes! Let the data and summaries speak for themselves.
And don't miss what happens when you shoot with an OM-1n instead of a OM-4.
*********
250mm f/2 Zuiko (multi-coated)
Vignetting = C @ f/2, A- @ f/2.8, A @ f/5.6
Distortion = None
OM-4 w/ mirror and aperture prefire via the self-timer
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+
Note: 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. Clearly one of the best
Zuikos made. Brillant images, with f/5.6 showing a corner to corner clarity
unsurpassed by any Zuiko tested to date.
OM-1n with mirror lock-up and self-timer
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
Note: 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 the 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 used the same lens.
250mm f/2 Zuiko with Olympus 1.4x teleconverter (both multi-coated)
OM-4 w/ mirror and aperture prefire via the self-timer
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+
Note: Moderate to moderately high contrast. Exceptional wide open
performance.
250mm f/2 Zuiko with Olympus 2X teleconverter (both multi-coated)
OM-4 w/ mirror and aperture prefire via the self-timer
Vignetting = D? (distinct central hot spot) @ f/2, B @ f/2.8, A- @ f/4
Distortion = slight pincushion
Aperture Center Corner
f/2 (4) D C
f/2.8 (5.6) B C
f/4 (8) B C
f/5.6 (11) B- C
f/8 (16) C C+
f/11(22) B- C+
f/16 (32) C C
f/22 (44) C C
Note: Not an Olympus recommended combination. Unusable at f/2 (effective f/4)
due to low contrast, poor resolution and hot spotting; moderately low
contrast at f/2.8 to f/4 (effective f/5.6 to f/8), moderate at f/5.6
(effective f/11) and beyond.
*******
Gary Reese
Las Vegas, NV
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