Polarizing filters test - supplement
2. Cokin Circ. Polarizer 72 mm
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Although the Cokin company is associated by every photographer with a rectangular filters system it also manufactures circular screw-on filters. We already know that Germans and Japanese can produce good polarizers. What about the French?
Results of the test
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Red color extinction coefficient: 2.50E-2 - Score: 0.5/4
Green color extinction coefficient: 3.87E-4 - Score: 3.5/4 Blue color extinction coefficient: 1.84E-3 - Score: 2/4 Mean transmission of the whole spectrum: 38.35% - Score: 2.67/3 Score:
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With filter Score:
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Luminance: 25.37
Score:
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 Edge darkening: 5.55% Score: |
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Significant streakiness
Score:
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Usage
You should be very careful when you attach this filter to a lens. The thread seemed too big and it resisted when we want to attach it to the lens. Next problem arose when we wanted to unscrew it – it got jammed. The thread is not the only issue here – while working in the temperature close to 0oC the ring moved very stiffly. The mechanical side clearly needs improving.
Summary:
Final result: 20.76/37.5 points. The Cokin would be placed at the very end of the overall ranking (18th place) and, unfortunately, this place is fully deserved. The polarizing filter’s properties are not bad. The transmission curve is flat in the visible spectrum. The extinction coefficient of 1/10000-1/1000 is also a good result. From 700 nm the filter lets pass the red light of polarization perpendicular to its azimuth. It might warm the extincted reflexes. The mean transmission reached a very decent result of 38%. The C1 and C2 graphs indicate that we’re dealing with a zero-order quarter-wave plate designed for the middle of visible spectrum. Unfortunately significant flares, streakiness and high vignetting lowered the score.It’s also a pity that the quality of workmanship leaves plenty to wish for. The ring stiffness, quite significant right now, can be diminished over the time but a jamming thread is really a cardinal sin. I suppose nobody would want a lens with a polarizing filter fixed permanently to it.
The tested filter was lent courtesy of the Antymex company.
