I am looking into purchasing some 4x4 filters. Does anyone know of any good kits or individual filters? What filters work best with the XL2?

Hi Alex,

for a start I would recommend a circular polarizer and one or two graduated ND filters, e.g. 0.3 and 0.6. If you can't afford both NDs, I suggest you go for the 0.6 as it seems more useful than the 0.3 (just my feeling). The graduated ND filters usually come in two versions: soft edge and hard edge. Personally I find the hard edge filters more useful.

I bought Schneider filters. They are very good but awfully expensive. But they will probably outlast my XL2 by many years.

Alex,

I use 4x4s by Formatt, who also make a decent affordable aluminum matte box to put them in. It has one fixed stage and one rotatable stage.

The filter glass is by Schott, the German optical company, and is gorgeous. The one filter I would put above all the others, is the Polarizer. I've even been known to use it on interiors.
http://www.formatt.co.uk/glass/filter_polariser.asp
I also use Black Supermist and Clear Supermists to add a bit of softness to the image.
http://www.formatt.co.uk/glass/filter_smist.asp
And another filter I like very much, is the Warm Tone Enhancing Filter (Skin Tone Enhancer). It really does make your talent look better, especially after a long winter of pale skin.

The filters and matte box are distributed in the U.S. by Bogen, and can be purchased at B&H, among other places.
Filters: http://www.bhphotovideo.com/bnh/controller/home?A=search&Q=&b=1548&mnp=0.0&mxp=0.0&cmpsrch=&cltp=&clsgr=&shs=Formatt&ci=1&ac=&Sub
Matte Box: http://www.bhphotovideo.com/bnh/controller/home?A=search&Q=&b=1548&mnp=0.0&mxp=0.0&cmpsrch=&cltp=&clsgr=&shs=formatt+matte&ci=1&ac=&Submit.x=13&Submit.y=8&Submit=Go
This is a picture of my XL2 rig.

Deleted my post.