was surprise to see many dust spots on my ND filter even thought it was kept in the box that comes with the ND filter
have tried to clean using micro fibre cloth but only managed to clear away some but still have some stains
thanks for the heads up.
so my lens thread size is as follows
35mm - filter size 52mm
18-105mm - 67mm
17-50mm filter size - 72mm
11-16mm - filter size 77mm
seems that a 62-77mm step up ring would be more appropriate, pls correct me if i am wrong.