Act12 gives great information. A lens hood provides good protection for the lens, in addition to sometimes improving photographs, Get to know when to use or not use a polarizer. It is the most useful of all filters. As for UV filters as lens protectors, I don't use them and have retired two lenses because of crude cleaning in the field. The cost of replacing those lenses was a tiny fraction of the cost of film they exposed over many years. Any adverse effect from using a UV filter is rarely noticeable, and they are a lot cheaper than lenses.