Denny G wrote in post #2378393
Polarizer.......Canon Circular PL-C and PL-C II.......For the same reason I buy Canon lens.
Whilst that logic makes sense, I also believe it's a bad choice. The Canon filters are nothing special - supposedly they're rebranded Tiffen and not multicoated. The only time I'd use a Canon brand filter is a drop in on a super telephoto (not that I own any lenses big enough to have drop in filter capabilities).
For screw-in filters I buy B+W, opting for MRC if it's available. Other good brands are Heliopan (opt for SH-PMC if you can) or the higher end Hoyas that are multicoated.
For holder based systems, you have a choice on format - is Cokin P series wide enough, or would you be better with the 100mm Lee format? I believe, but am not completely sure, that the Cokin Z-Pro holder is the same 100mm size as Lee. Meanwhile, Lee filters can be ordered in P series format.
Once you've decided on format, and which holder you want to buy for that format, you then need to buy filters. Cokin's ND grads apparently aren't neutral, but other brands are available that are more neutral.
David