Filter on digital: Clear / UV

[Erik Lund]

Ditto. After film was over no more filters.
Yes always a lens hood on!

The sensor cover glass surface is reflective, film was not.Yes, the light reflected off the sensor cover glass and reflected out through the lens can hit the inside of the filter and reflect back, especially at night.

[Bruno Schroder]

Lensrentals has a very good article on transmission spectrograms of (some) UV and clear filters: https://www.lensrentals.com/blog/2017/09/looking-at-clear-and-uv-filter-spectrograms/

This other blog post has links to a bunch of other articles they wrote about filters. Worth a read. Check the first paragraphs for the links: https://www.lensrentals.com/blog/2017/06/the-comprehensive-ranking-of-the-major-uv-filters-on-the-market/

My personal conclusion: like Birna: hood, polarizer or spray protection.