I have been trying to clean my 77mm Hoya HMC filters. Can't seem to get it perfectly clean. It's driving me crazy. Anyone out nows how to get them pristine clean.
The usual methods of Microfibre cloth and a blower are pretty good. If your filter was wet, wait for the water to dry first or put it in a dry cabinet. Try not to use solutions as these sometimes leave marks. In some cases, you may even damage the coating on the filters. Try not to clean too much as this will also wear down the coating.
Tried using my micro fiber cloth. I also tried lens pen. No matter how I clean I see swirling marks. You can only see it if you tilt it slightly in the light.