I just got an IR filter along with a cokin filter holder. When ever i use it i can see the reflections from the elements inside the lens on the picture. Im guessing this is because light is bouncing to and from the inside of the lens and the filter because i just held it to the front of another lens and i didnt seem to have this problem. Im wondering if its just because the lens sucks, its a sigma 18-200mm and im looking to replace it very soon so it aint the end of the world if i have to wait a lil longer to do some IR photography but and ideas on stopping this problem would be a great help!!!