Originally posted by TaoMaas You're going to find that there's an equal number of folks on either side of this question.
Indeed so.
A good filter won't degrade quality much, but "Scientifically" speaking, you are adding another layer of glass in front of your expensively engineered lens, and that definitely makes a difference. If you can notice it or not, will be the thing.
On my 18-50, the uv filter (a cheap kenko) makes no difference, and my tests have shown it to be of no consequence.
However, on my 70-300 apo, the more expensive sky light im using, definitely affects my quality (tested twice)... strange, I know. Either way, for the little IQ I lose, I leave it on for _most_ purposes, and since the filter saved my front element at an offroad biking event once, I like having it there.
And yes, stop pixel peeping, it's a sin.