Polarizer Filter Mini Test

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.

Tested Filters

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
  • Resolution impact (update). Do these polarizers impact resolution? Only tested on Hoya and B+W because I no longer have a lens usable with the Soligor

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.
Polarizers, tint and density

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

 

Polarizers, transmittance

Transmittance calculated from method 2.

Tint

Polarizers test, tint

Result 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

Polarizers test, tint - sky color

Sky tint.  Camera exposure was set to auto, no individual corrections were made on the raws.

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

Green Foliage

Polarizers test, tint - foliage color

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.

polarizers-color

Contrast

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

Resolution Impact (Update)

Resolution impact was tested with Zeiss Macro-Planar lens at f/6.7 and f/4 on near infinity and approx. 6ft. I see minimal or no impact.

CPL test - Resolution impact at near infinity

Resolution impact at near infinity. Actual pixels from 21MP FF camera.

 

CPL test - Resolution impact at approx. 6ft distance

Resolution impact at approx. 6ft distance. Actual pixels from 21MP FF camera.

The Mount

  • B+W mounts are made of brass, the other filters are made of aluminum. I found that the the B+W filters tend to stick a little bit in my Canon lenses and work perfectly on Zeiss lenses. The Hoya HDs are fine on Canons, but stick to Zeiss lenses and is some cases are difficult to unscrew
  • The thin Hoya HD has very little material on it and compared to B+W looks more delicate
  • I have been using the Soligor filter for some 20 years now and never had any issue with it on any lens
  • None of the filters came apart on me

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

This is not a comprehensive test and I will not rate these filters. But I hope some of the collected data can help you in your decision.

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