Do you have any evidence for filters degrading an image?
I'm not being argumentative, just honestly asking for evidence as this is an oft repeated thing and I've honestly never seen anything even remotely noticeable but maybe I've just been lucky with uv and other "protection" filters. The only issue I've ever seen is when there's a light in the frame for eg nightime shooting and streetlights and that can be a real issue.
In my dslr days I had a filter of some sort on any lens that'd take one but these days I don't bother.
Putting a UV filter on the Panasonic 100-300 has a huge impact, I still don't know why, but it was suggested that it is the effect of having another glass surface close to the front element.
Loss of both contrast and sharpness.
Reviews say that the 100-300 is not as sharp as the 100-400, and at first I though this was the reason, but when the last discussion about using UV filters came up, I removed it and compared again, and it changed the 100-300 completely.
I tried two reasonable quality filters, and both had a similar effect, yet the same two filters on a Canon lens had no noticeable effect.
Putting a UV filter on the 100-400, or any of the other Panasonic lenses has no noticeable effect.
Probably my UV or most usually skylight filter probably did go back to film, as up until 20 years ago, most of my photographs were take nearer to the equator where blue was the usual colour of the sky not grey

. The four most available films were Kodachrome, Ektachrome, Agfa and Gratispool (all had to be sent away for processing, and took about 6 weeks), and particularly Agfa had a very noticeable blue cast without a skylight filter.
In nearly 60 years of using a camera, and 50 years of interchangeable lenses, I have never damaged a lens, however I am finding to start not using a UV filter entirely is a hard change to make, although I can see the logic in it
