>>4057165That occurred to me as I was lying in bed and I felt like a retard for not thinking of it immediately. I cut a 10mm hole in some opaque plastic, then tried it both in front of the lens and sandwiched between the lens and the adapter. Actually seems like it worked. Darker, sharper, and the DOF widens up. Behind the lens works especially well, where I could probably get better results with a smaller hole, without all the vignetting I got from putting it in front of the lens. Pic related. Cool to know, but not helpful. Swapping holes out on the fly isn't practical for my purposes.
>TL;DR>hole in front of the lens works okay, but vignettes too much>hole behind the lens works perfect, but can't be adjusted without removing the lens 