Originally posted by BruceBanner I must be an idiot (I mean I know you all know this already )
This happens to us once in a while
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For ND filters, I recommend wet process. Since ND filters are free of electronics, I clean them like my glasses, that I learned from glass manufacturer.
I soak (no rubbing) my filters in a clean warm (not hot) water with a drop of dish wash liquid, two times, rinse with plain water, dry, and finish drying with a clean microfiber cloth, they come out like new.
Never rub the glass when in water solution since there could be some particles scratching the coated surface, only soaking a few times is enough for dust and greasy finger prints to dissolve in the cleaning solution.
Fingers are naturally greasy, even freshly washed. Wearing latex gloves to manipulate the filter during the cleaning process eliminates chances to leave finger prints on the clean ND filters again.
Typically, people use a microfiber cloth directly with bare hands so fingers gradually deposit oily substance on the microfiber cloth , after a few uses the microfiber cloth isn't working anymore. So use latex gloves, wash the microfiber cloth and don't touch it with bare fingers again.
Last edited by biz-engineer; 03-03-2020 at 12:06 AM.