Hi everyone,I have a Hoya HMC 67mm UV filter.Recently I noticed some "grease or oil-like"patches on the filter itself.You have to tilt the filter to a certain angle before the patches is noticeable.I have tried cleaning the lens but i only manage to clean some of it.My friend commended that it is some kind of grease or oil kind of thing but i am clueless.But however it doesn't seem to affect the IQ in any way.& sorry guys,i have tried following the steps to post the image but i got lost halfway thru...So to all brudders what should i do now...is there any kind of cleaning solution or any way to get rid of the grease-like patches?i am still wondering how the patches can be stuck in the filter & also where is the source?Pls help & thanks very much!