I usually use Hoya and Tiffen 81A and 85C filters for my slide work.
They work well with all my lenses except with my Nikon 20mm f/4, which vignettes.
I know that Nikon filters are thinner and work well on this lens, but the Nikon A-2 filter is nowhere to be found.
Who makes 81A and 85C filters that are thinner than Tiffen's and Hoya's?