B+W polarizers have great reputation and I always thought about them as the automatic selection for my lenses. However, I needed new slim  polarizer for my UWA lens and B+W did not work well for me this time, because the slim version was needed and slim B+W filters don’t have front thread, which I find annoying. I looked at competition and decided for Hoya HD. Now I have several brands of CPL filters, which is a great opportunity for some comparison testing.

The Contenders

• Hoya HD CIR-PL 82mm
• B+W Kaesemann Circular Polarizer 77mm
• B+W Kaesemann Circular Polarizer 72mm
• Soligor C-P.L. 58mm. This is a circular polarizer in aluminum ring, apparently with no coatings (not anymore, anyways). It is 15, maybe 20 years old and I could not find any specs

The Test Objective

This is not attempting to be a scientific test and is not conducted in laboratory conditions. Tested filters have different sizes, have different age, everything is tested on a camera with 50/1.4 lens with larger filters fitted with an adapter ring. No lens hoods were used. Transparency/density test was repeated twice, other tests were run only once. Areas of interest were:

• Density. How much light the different polarizers block
• Tint. What kind of tint the filter have, if any
• Strength of the the polarizing effect. Is weak polarizing effect the price for better transparency?
• Look of the green and blue polarized areas. Do the filters create equally pleasing greens and blues?
• Contrast. See how different filters impact contrast f no lens hood is used. Lens hood could not be used due to different sizes of filters used in the test

Testing And Results

Density

Density was evaluated by two methods:

1. With filters placed on a transparency light table, every filter placed at the same location of the table to eliminate unevenness. Power voltage fluctuation was around 0.5% during the test. The filter was shot with a macro lens with camera in manual setting. The images were brought to Photoshop and color balance was set to 5400k, which is the “paper” color temperature of the light table. Center of each filter image was then cut in Photoshop and placed in a composite image for visual comparison
2. Diffuse white wall was photographed with the filters on. Each filter was turned to make sure there is no influence of the polarizing angle. Two different walls were used and exposure readouts collected and deltas between no filter and filter on averaged.

Outcome of the first method. Comparison of filter density/transmittance. Four identical manual  exposures of 4 different filters on a light table. White balanced to the color temperature of the light table.

Outcome of the second method. Number of f-stops needed to achieve correct exposure  compared to lens with no filter.

Filter	Stops (approx.)
No filter	0
Hoya HD	1
B+W Kaesemann 1	1 3/4
B+W Kaesemann 2	1 3/4
Soligor	1 1/2

 

Transmittance calculated from method 2.

Tint

The outcome of the Transparency 1 test served as an evaluation target for tint. The following image is the same as above, but with increased saturation to show the color of the shift.

 

Strength Of The Polarizing Effect

Strength of the polarizing effect was evaluated from pictures of a plant with waxy leaves. The pictures show no significant difference between the images. 

Color of Polarized Sky And Foliage

Sky

This is a crop from the darkest corner taken with different filters. Camera exposure was set to auto, no individual corrections were made on the raws – all processed the same way.

The strength of all filters looks very similar. The yellowish tint of Hoya is clearly visible in the sky  (and clouds).

Green Foliage

This is another crop from the same field, showing green foliage. The same processing conditions as above.

The yellow tint does not seem to bother here.

The following composite shows the whole picture from which the above crops were taken. The white balance is equalized, this time.

 

Contrast

Contrast was evaluated on pictures taken without lens hood. The differences are subtle, Hoya HD seems to give the same or better contrast as the Kaesemanns, the Soligor shows discernibly lower contrast than the others. The Soligor has apparently  no coating and therefore this behavior is not a surprise.

Conclusion

The above mini test shows behavior of three different brands of filters and sample variation between two B+W polarizers. Let’s sumarize the major findings:

• The Soligor that has no coating shows discernibly lower contrast when used without lens hood. On the other hand, the other qualities are similar to much more expensive filters
• The B+W Kaesemann shows some sample variation, more than I would expect with premium filter. The polarizing effect and resulting color is about the same as the other filters
• The Hoya HD passes 3/4 EV more light than the B+W, which is nice. It is very thin, but still has a front thread, which is very nice. The polarizing effect and contrast seem to be on par or perhaps better than the B+W. The yellowish tint may require one extra step in post processing

The test does not say anything about sharpness, flare, quality of the mount, ease of maintenance or durability. Without these parameters I’ll avoid rating these filters.