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Polarizing filters test

10 August 2009
Szymon Starczewski

9. B+W EW KSM C-POL MRC 72 mm

Polarizing filters test - B+W EW KSM C-POL MRC 72 mm
Polarizing filters test - B+W EW KSM C-POL MRC 72 mm
B+W EW KSM C-POL MRC 72 mm
Price: 559 PLN


B+W filters are manufactured by German Schneider Optics and definitely don’t belong to the cheapest ones. They’re covered by hard, thin MRC coatings which protect them against scratches. The respect of photographers, that these filters have, should go hand in hand with the highest quality.

Results of the test

Transmission and extinction coefficient
Polarizing filters test - B+W EW KSM C-POL MRC 72 mm

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Red color extinction coefficient: 2.94E-4 - Score: 3.5/4
Green color extinction coefficient: 3.04E-4 - Score: 3.5/4
Blue color extinction coefficient: 9.81E-3 - Score: 1/4
Mean transmission of the whole spectrum: 35.55% - Score: 2.11/3
Score:
10.11/15
Flares
Without filter
Polarizing filters test - B+W EW KSM C-POL MRC 72 mm

With filter
Polarizing filters test - B+W EW KSM C-POL MRC 72 mm

Score:
7.5/7.5
Scattering
Polarizing filters test - B+W EW KSM C-POL MRC 72 mm

Luminance: 18
Score:
4.89/5
Vignetting
Edge darkening 3%
Score:
3.89/5
Homogeneity
Polarizing filters test - B+W EW KSM C-POL MRC 72 mm

Without reservation
Score:
5/5
Final score
Overall ranking: disqualification
Econo-ranking: not included
31.4/37.5 pts (83.7 %)
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Usage

The ring turns smoothly with an appropriate resistance, you can hear delicate swoosh. The filter is well-made. During the tests there were no major problems with it.

Summary

The most points in the overall ranking (31.4/37.5) and disqualification. The transmission of the polarizer is quite flat in the majority of the visible spectrum. The extinction coefficient of around 0.3/1000 is a very good result. The polarizer becomes transparent in infrared. C1 and C2 graphs indicate that, either there’s no quarter-wave plate, or it was glue at an angle of 0 or 90 degrees against the azimuth of the polarizer. We’re dealing with a very good linear polarizer, although both on the box and on the ring, there’s something totally different written. It’s hard to guess if it’s a huge mistake and oversight from the quality control, or deliberate action. Whatever the reason, this should not have happened. For obvious reasons, the polarizer was omitted in the overall ranking.

Filter for tests was lent by Pstryk.pl