Here are the results of a paired SQF lens test of a late production 50mm
f/1.4 Zuiko, with and without a poorly made Vivitar VMC filter. As expected,
there was significant image deterioration with the filter. Note that image
deterioration intensified with larger apertures.
********
50mm f/1.4 Zuiko (multi-coated)
OM-2000 with mirror and diaphram prefire; lens with >1,000,000 serial number
Vignetting = D @ f/1.4, B @ f/2, A- @ f/2.8, A @ f/4
Distortion = none
No filter
Aperture Center Corner
f/1.4 B B
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 B+ B+
Note: High contrast, except moderate in center at f/1.4, moderately low in
corners at f/1.4 and moderate in corners at f/16; remarkably even performance
across all apertures.
With poorly made Vivitar VMC ND3 neutral density filter
Aperture Center Corner
f/1.4 C- C
f/2 C C
f/2.8 B B
f/4 B B+
f/5.6 A- A-
f/8 A- A-
f/11 A- A-
f/16 B+ B+
Note: Differences are significant at the 1/3 grade level in this paired
comparison evaluation. Contrast was slightly lower with the filter, but lower
resolution was the most important factor in image deterioriation. Please
note that this particular filter is not indicative of Vivitar or Vivitar VMC
filters, in general. It was simply a poor sample. Other filter makers, even
the most highly regarded, have been found to have poor samples in selections
taken from used and new stocks of filters. The use of the term "poor" means
star test images on a collimeter which show multiple overlapping images,
fuzzy images, off center images and images which rotate when the lens is
rotated. More often than not, only one of these faults are found in an
examined filter. These filters (including the test filter) often look
perfectly good when examined without the aid of instrumentation!
*******
This is a draft version of what will be posted to my Zuiko Lens Test site.
It still needs editing, but the data won't change.
Gary Reese
Las Vegas, NV
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