i just bought a new B+W polarising filter for my 350D last week.
even before i get to use it, i left a ugly fingerprint on it.
so i proceed to clean it with a specatcles cloth.
the fingerprint is removed with ease,
then when i started to clean the rest of the filter, smudges began to appear!
when i look at the cloth, it's stained with alot of black oily marks.
after some close examinations, i realised the dirt/oil came from the filter's inner threads.
i happened to rub the cloth against the threads,
and i cleaned the filter using the same spot of the cloth..
now the filter looks like post-WWII filter...
just wanna ask u guys..
is it normal for filter's threadings to have lubricant of some sort?
is there any basic technique to cleaning filters?