I bought a screw-on 10 stop ND filter to use with a 150mm ssxl lens and I exposed 4 sheets of 7x17 HP5 sheets last weekend. I rated the film at 200 and metered the scene, rocks and ocean in the sunlit afternoon, through the filter and I came out of my darkroom two days ago with 4 blank sheets. I mean, nothing at all! No light hitting the film at all for the entire 2 minutes at f/45.

Anybody have experience with these 10 stoppers? Maybe I will try to use it with my WP camera first and double the exposing time. I hate to waste large sheets of film.