Originally posted by Tom in Delaware I would rather have a scratched UV filter than a scratched front element and I have had a couple of filters take the brunt of branches or table corners. A good filter is optically flat and won't degrade image quality to any measurable extent. I like Hoya HMC filters, these have an excellent multi-coating and a relatively thin profile.
The Lenstip site did a nice comparison of multi-coated filters and Hoya HMC came out on top although they were not the most expensive brand tested.
Oh yeah, I've done that too! Particularly shooting macro; focusing in on one blossom amidst a cluster of them, with such a narrow field of view it's easy to forget another blossom could be closer to your lens than the one you are trying get and smoosh! Sticky pollen dust all over the front of the lens, that's when I thank the deity for filters.
Thanks,