So, i bought a pentax 50 MM f/2, and now i am looking at filters. I bought a polarizer filter (this is the same as a neutral density, right?) today, and im just wondering if there are any others that i should think about purchasing, that would improve my photo's. I play on taking pictures of animals (birds) as well as scenery shots and sunsets, and water pics. thanks. Also, just wondering if there were any websites that had a list of different filters and what they do.