I have been thinking of buying a circular polarizer and I have a couple of questions. 1) I have heard good things about warming polarizers and kaeseman polarizers, but what is the real difference between the two and can you recommend one over the other? 2) So far, my largest lens is 67mm. Should I get a 77mm polarizer and use step up rings so that I would be able to use it on any lens that I would probably ever own, or is it better to buy a filter that is the same size as your lens? Also, are there any brands that I should stay away from?