Circular Polarizer Filter $15 to +$100

[TakahiroW4047]

I'm thinking about getting the filter for my Tamron 17-50mm (67mm). From what I can gather from production description and the review of the B+W filters right here on this site, it's better to get a better quality filter so not to degrade the image quality achieved by the lens...


By "degrade" what kind of distortions are they talking about? The most mentioned seemed to be flare control with multiple lens coatings. Are there others involved? CA, Contrast, Sharpness? I'm trying to see if the added cost of having better build quality, multiple lens coating vs not so rugged build and no coating is worth it?Will the "degradations" even be noticeable? I think I can live without the ruggedness and good sealing because the only "weather-sealed" gear I own is the 7D and maybe the LowePro bag [:P]

[neuroanatomist]

By "degrade" what kind of distortions are they talking about? The most mentioned seemed to be flare control with multiple lens coatings. Are there others involved? CA, Contrast, Sharpness?

Generally, flare is the main issue with low-quality filters. Keep in mind that there are several 'flavors' of flare, not just the obvious kind seen when shooting into a light source. Veiling flare, resulting primarily from light reflecting back into the lens from the internal surface of a filter, causes loss of contrast. Another possible aberration is loss of sharpness if the filter is not optically flat (astigmatism).


A CPL is a great filter to have, but not one to leave on your lens all the time (keep in mind it causes loss of 1.5-2 stops of light, and also at the 17mm end of your lens with a wide expanse of blue sky, you'll probably see some banding due to partial polarization).

[TakahiroW4047]

You convinced me. I decided not to cheap out and went for the Hoya HD Circular Polarizer off of Maxsaver [] Thanks as always!!

[peety3]

A CPL likely has a layer of polarizing material surrounded by two layers of glass. Better filters will ensure that the material is properly sandwiched between the glass, and some will ensure weather sealing for the inner layer.


If the glass layers are not "perfectly" flat, refraction of light will occur, causing some of the degradation. You'll also have four "flat" surfaces that can reflect light in unexpected ways.


Good luck with your filter purchase.