[timjon]

I was taking some photos of a rather violent sea recently, with the result that pretty much everything got coated with an occasional spray of salt water.

I had a UV filter on the lens, so the front element is fine, but I'm now struggling to get the filter itself nicely cleaned. I've tried using mild detergent and warm water, which works fine to get the filter clean, but it then dries with faint water spots all over it.

Any suggestions on a good way to get the filter back to its original "invisible" cleanliness? It's a 72 mm Hoya Super HMC, so a bit expensive to just buy a new one!