I am not a big fan of using UV filters for general photography unless the environment calls for it such as sand or flying objects; however, I am a big fan of using circular polarizers when shooting water or other reflective surfaces.what is a polarizer? I am not a physicist so I am sure there are many other websites and books that explain it perfectly, but in layman’s terms light that hits a surface is very disorganized due to bouncing off of many different surfaces. In the example above for instance, the light that is hitting the water is bounced off clouds, trees, and many different surfaces.
A polarizer takes this on organized light and aligns it into it well defined beam which block out other polarizations. I can’t even begin to explain how it does this but I don’t need to know. What I do know is that many photographers needlessly leave their CPL on their camera at all times. That is a stupid thing to do because it robs about 1 1/2 stops of light. At a wedding a couple of months ago, I ran into a guy I knew from college and on his Nikon D3100, he had a CPL on the kit lens. I tried to explain to him that he was robbing his camera of so much light that is flash would have to work extra hard but he told me that having it on makes pictures look more the way they are in real life. I think exposing the pictures correctly in the first place is the better solution.