I just put one on my 15-85 and did some test shots outside. While I'm looking through the viewfinder should I be able to definitively tell where the filter "is". I had my camera pointed at the sky and was rotating but could not tell where my polarization was. It has about 2/3 of the edge of the filter grooved so I assume that means something but what.
It appears from looking at the pics on the computer that the smooth portion is the CPL areas. Is that right?