How to clean the filters if there is oil stain on it?


Spray lens solution cleaner onto it, use the micro fibre cloth to wipe it off. You could use a lenspen after doing that. :)
 

wash with soap and clean with a cloth
 

Use a good quality lens cleaning liquid and spray it on the cloth and gently wipe it off..Lenspen can clean tiny smears not if it's a big droplet.
 

wash with soap and clean with a cloth

yes, that is the best way, i try that before on a few filters, works great, very clean, totally no greasy thing anymore on the filter, after cleaning with soap and water, the filter will be less prompt for dust since there is no oil on it. then use a clean cloth to wipe it dry, tshirt should be able to do the task.
 

This is what I do:

1. 1st gently rinse with flowing water to get rid of any solid particles that can scratch the lens.
2. Apply soap
3. Wash off the soap.
4. Flick off the water
5. daub off water droplets using either crumpled newspaper or lens tissue
6. Leave under fan or sun to dry.
 

wash with soap and clean with a cloth

ah... why no one gave me this tips earlier... i almost sold all my filters just because it's such an hassle to clean...

IMO cleaning lenses front elements are easier... ;p

Thanks for good tips... :D