Photography Experiment: UV Filters Don't Hurt Quality

Do UV filters hurt quality? Some people say so, so I decided to find out for myself. I took photos with my 19mm lens with the filter:

... and without:

(Right-click each photo and open in a new tab full-sized to compare them)

I see no difference at all between them, full-screen on my 5K iMac.

I repeated the test with my 35mm lens, with the filter:

... and without:

And with my zoom lens, with the filter:

... and without:

The filter makes no difference, for any of the three lenses. You can use UV filters to protect your lens, without worrying about any loss of quality.