filter

Hi I went to shoot with an # 2 ND filter yesterday and all the shots were overexposed. I can post samples later. What did I do wrong? My only guess is the auto iso.

Greets; hopefully this generates some advice. I have an older telephoto lens with 72mm front filter thread. I need to remove the trim ring to access the front element. I can buy a set of the rubber tools to do that, but I can't find just a 72. Any suggestions as to what sort of cylindrical...