Polarising filters

Yup, though for it to work you'll need to put the front one on back to front - i.e. you need the front of each CPL facing each other. It's easier to just use a CPL mounted to your lens and a linear PL filter hanging off that - that combination will work fine too.
 
Brian's right. Also you may find, depending on the lens, that you will get some severe vignetting.
 
You really need one circular and one linear polarising filter. It works pretty well up to about 5 seconds in full daylight.

Put the linear in front of the circular.. so it goes camera-lens-circular-linear.



You can get a reasonable colour correction, it's just that the best two I've uploaded aren't colour.
 
Alastair said:
You really need one circular and one linear polarising filter.
Click to expand...

Nope, as I said, it works fine with two CPLs once they are orientated correctly. Since you are using crossed polarisers in any case, you can't really use the polarisers as polarisers in this setup. So the only loss to using a second CPL is the extra faff (since the filters will be mounted fixed thread to fixed thread with a reversing ring) and a small amount of additional light loss due to the quarter wave plate (which anyway people don't seem too worried about since they tell digital users to always use a CPL despite many cameras working fine with linear polarisers)
 
From experience, I would still recommend a CPL-LPL combination.. if for no other reason than it's a helluva lot cheaper to buy a LPL than a second CPL and a reversing ring. If, as you seem to be saying, it's all the same anyway.
 
It works in theory, but in practise you get that characteristic dark cross pattern appearing at higher densities with wide angle lenses, as the two polarising foils clash. Not that you can use really wide lenses with a set up like that, due to mechanical vignetting.

And it's also expensive whichever way you do it, and quality isn't great. Might as well get something like the LightCraftWorksop Fader ND, which is about £80-100. I sent mine back though, and now use their ND500 fixed ND, which is pretty good.

Edit: Fader ND review here, though I can't get the link to load ATM http://www.ephotozine.com/site-search/fader-nd
 
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