I have no experience with polarizers. I tried "Cir Polarizer Korea". Box comes from "PRINZ". Description promissed "enrich color", "eliminate glare", and other desirable effects. I made a 100 test photos of various lighting and reflections from water, glass, metal, using Nikon 50/f-1.4 and Nikon 85/f-1.4. It does not matter how I rotated the filter as it was not making any difference. All 100 photos are much softer than photos without the filter, and colors look "dirty". I think this filter should be advertised as a soft focus diffuser, but I am not sure if it would qualify as a Neutral Density filter since it does add some darkness and colors look dull and dirty. I would like to make photos with more vibrant colors and higher color contrast in the sky, like many photos presented in this forum. What filter should I purchase?