(multi-coated) 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 = slight barrel Aperture Center Corner f/1.4 C C f/2 B B f/2.8 B+ A- f/4 B+ A f/5.6 A- A- f/8 A- A- f/11 B+ A- f/16 B+ B+ Notes: Moderately high contrast, except moderately low at f/1.4, moderate at f/1.4. 50mm f/1.4 Zuiko (multi-coated) OM-2000 with mirror and diaphram prefire; lens with >1,100,000 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+ Notes: 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+ Notes: 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 just tested as 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, viewed on a vertical auto collimeter, which show images that are: multiple and overlapping, fuzzy, off center, 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! 50mm f/1.4 Zuiko (multi-coated) OM-1 with mirror lockup; >1,000,000 serial number (different lens than above tests) Vignetting = B- @ f/1.4 Distortion = moderate barrel Aperture Center Corner f/1.4 B B- f/2 A- B f/2.8 A- A- f/4 B+ A- f/5.6 A+ A f/8 A A- f/11 A- A- f/16 A- B+ Notes: Moderately high contrast with remarkably even performance across all apertures.