I have recently written an article about how to use a polarizer with the Nikon 14-24mm f/2.8 and the Lee SW-150 holder. The drawback was the limited selection of polarizers. The only available CPL at this time was the Cavision which is rather expensive and inconvinient to use at it is 4mm thick.
At Photokina 2014 I found an alternative CPL from Nisi Digital. As you might already know it is not possible to rotate the polarizer independently of the ND grad filters in the Lee Holder. That makes it essential that the polarizer delivers full polarization in either straight or 90° rotated orientation. Unfortunately my tests with the Nisi CPL showed me that this filter gives full effect only in 45° orientation. A no go for everybody that wants to use CPL filters together with ND grad filters.
I have been discussing with Nisi about this issue and fortunately they have now developed a new version of the 150mm square CPL filter. Version II has now the same polarizing axis as the Cavision polarizer. Due to it’s thickness of only 2mm and it’s lower price tag compared to the Cavision polarizer it’s a no brainer and I can highly recommend the Nisi polarizer. In terms of the Lee SW-150 holder the filter fits perfectly into the standard 2mm guides. Light reduction is somewhere around 1,3 stops.
You can buy the Version II Polarizer from this Link.