Somehow I had parked in my memory the idea that it was a good to keep a UV filter on my camera, at all times. To keep the underlying lens from getting dirty. Is that "ok" or am I going to be screwing up my photos now? If it's not ok -- is there some sort of "neutral" filter that you can keep on a lens all the time, to keep it from collecting dirt/dust? Sorry for the seemingly stupid question...I am a total newbie at this.