I know I am beating on a dead horse. This topic has been discussed to death already. To use or not to use protection filters. Why and why not?
My friend Cliff recently bought a B+W Graduated Neutral Density (Grad ND) filter and reported that there is excessive flare when using the filter. Personally, I am not a filter person. Most of my lenses, even the most expensive ones, are naked. I am in the school of thought that when you buy a $2000 lens, why put a piece of glass in front of it that was not part of the lens design? The opposite camp will argue that filters will protect the front element and it should not cause any adverse effects on the image quality.
Well, horses for courses. You do what you think is best for your investment. For me, my thinking is that filters in most cases will not affect the image quality, except in very challenging lighting conditions. To illustrate, I have two pictures I took couple days ago. One with, and one without a UV filter.
Picture taken with JML 50mm f0.95 lens and 62mm Rodenstock Coated UV filter. Larger Picture.
Look at the picture above. The circled area are reflections. The double green dots are reflections of the car head lights, and the single dots are reflections of the traffic light. I have a couple more with more double dots, each set corresponds to a car's headlights.
Same scene without filter. Larger Picture.
The picture above is without a filter. You can see that there are no reflections that were present at the previous picture.
My suggest? Do not use filters at night, at least not with point light sources.