Lots of vicious flamewars have been fought over whether to use UV or other protective filters on high end glass -- whether there is any loss in image quality, and whether it is worth it.
But how about this: what about using a good, multicoated filter on older lenses prone to flare? Can a multicoated filter actually improve the image quality of an older lens that has few coatings, if any, or coatings damaged or worn away by years of cleaning?
I have several 50+ year old Leica and other lenses, that are supposed to be prone to flare, etc., and I'm wondering if it would improve things if I put a filter on them.
Summar 5cm f2
Summicron 5cm f2
Elmar 5cm f3.
Culminar 135mm f4.5
Jupiter-8 5cm f2
Jupiter-12 35mm f2.8
For that matter, I have some older non-Ai Nikon glass that may benefit, too. What do you think.