Before most of my camera gear was stolen, I had taken one test shot using a B&W ten stop glass screw in filter on a Canon 17-40L. It had a very warm cast. Now I am about to replace lens and filter, I wonder whether the Lee 100x100mm slot-in glass filter (at least I think it's glass - could be very high quality resin) might be a better idea, i.e. more neutral. Of course, if I decide to replace with 16-35 rather than 17-40, has to be slot in since don't make B&W 82mm screw-in.
Anyone used the Lee filter?