I agree with OldCarlos. I don't use a filter to protect the front element from an impact, however I do always use a lens hood.
I have had a filter save a lens a Sigma 24mm F1.8 dropped about four feet onto planings the filter shattered the lenshood snapped but the front element lived.
For 35mm / small format digitail for frequenty used lenses I tend to use a protective filter especailly if at the coast in high wind salt / sand being nasty stuff however if shooting into the sun I'll probablly take it off.
On MF or LF never but then they tend to get handled a lot more carefully.
A lot of petal hoods I find are not always especailly effective and strategacly positioning a hand can be more effective with LF the usually quoted option is to use a darkslide
Personally I would always fir a quality UV filter. In my opinion a quality filter does not have any noticeable effect on IQ, reduces haze and most importantly protects the front element. It is much cheaper to replace a filter than have the lens repaired.
Many years ago i bought filters and in a none too scientific test setup a tripod and shot various lens with and without filters in normal daylight conditions. Even pixel peeping i couldn't see a discernible difference in image quality, contrast etc. So i've continued to buy filters for my lens and use them when out and about, i recall Canon spec is weather sealing on an L len isn't complete without a filter attached.
Many years ago i bought filters and in a none too scientific test setup a tripod and shot various lens with and without filters in normal daylight conditions. Even pixel peeping i couldn't see a discernible difference in image quality, contrast etc. So i've continued to buy filters for my lens and use them when out and about, i recall Canon spec is weather sealing on an L len isn't complete without a filter attached.
i recall Canon spec is weather sealing on an L len isn't complete without a filter attached.