Filters & Sigma 10-20

I have purchased a used Sigma 10-20, which came with a UV and CPL.
I have used a circular grad filter on my Tamron 18-250, but from what I have read the Cokin system is superior to the circular ones.

So my question is do the Cokin system work with the Sigma (using a wide-angle holdall), and with the correct sized adaptor will work with the Tamron?

Also are there any issues with CPL's on the Sigma (don't know how good/bad the one I have acquired is)?

I'm very happy with the Hoya green coloured range on the Tamron, so would probably go down this route again.

All advice greatly appreciated.

Regards
Adrian

CPL's can be used with the 10-20. They may be an uneven effect from polarisation due to the vast angle of the lens. There may be some vignetting from a thick filter. The Hoya Pro ones are thin.

Cokin P and similar systems can also be used with this lens, though with vignetting at the wide end, unless perhaps the holder is modified.

Ther is also a Z-pro serie from cokin, you can reverse mount the filter holder so that you get a slim filter. The filters are also 100mm wide so filters from other systems also fit in it.

Z-pro is more expensive though but the filters are higher qualty then the P ones also.