After much research I've decided it's time to buy a polarizer filter. What I've learned over the years is to spend the money on quality products now and be done. There are numerous choices from a variety of companies. I have a Sigma 100-300 f4, Nikon 18-70, 35-70, 105VR. I'm planning on adding something on the wide end, maybe 12-24. And, as you know, this is a bit of an evolutionary process as our photographic skills and needs change. I'm wondering what you folks use/recommend. I appreciate any suggestions you might share.