Do CPLs cause a color caste?

[Kayaker72]

I had always assumed this was a given, as I read it on the internet (Link under "which one to choose"), so it must be true.

Below is a picture that I've always attributed to the color cast from a CPL (taken with B+W 72 mm MRC CPL):


Beach IMG_4075 by kayaker72, on Flickr

I processed the above shot using DPP back when I had just started learning post-processing (still so much to learn). So, I took another stab at it with lightroom 4 this morning:


small-4075 by kayaker72, on Flickr

That is getting closer to how the scene looked (it is a beach we go to every year), but still something is missing from the grasses. But it also took adjusting the color temp, saturation, vibrance, tone and yellow & green slider bars for both Hue & Saturation. And it still isn't quite right.

So, I am curious, anyone else feel that their CPL gives a slight color cast? I understand that in theory, the CPL is just blocking wavelengths, but I had thought practice was a bit different.

[Kayaker72]

On the way into work, I remembered that lenstip.com had tested CPLs:

http://www.lenstip.com/115.4-article...d_summary.html

But they actually state that the B+W MRC (ranked #6) that I use should be a little warmer, if anything. But blue does have a 5x greater "extinction coefficient" compared to red and green with the lower extinction coefficient being better.

JRW....that is one of the more extreme differences that I've seen using a CPL, but I can usually detect something. Plus, I like your idea of using a custom white balance. I'll try that, but was wondering if it changes as you adjust the CPL (rotate the dial)?

Thanks,
Brant

[Sean Setters]

I'm red-green colorblind and I can tell a significant difference in color when using my B+W 77mm Kaisemann CPL. The images are quite warmer using the filter. The best thing to do is use a custom white balance using a gray card if you do not like it. As the color change is global (consistent across the entire frame), the color change is [relatively] easily correctable in post if you do not set a custom white balance.

However, that top image seems to be suffering from uneven polarization more than anything else. Was the picture taken with a wide-angle focal length?

EDITED: Mine is an MRC filter. Go figure.