Silver Vespa -- NEX-5 & Bausch & Lomb Super Cinephor 4.75 inch f1.9. Click for larger.
Now that I have tried a few projection lenses, they all have one thing in common: all very sharp wide open, and all purple fringing like hell in highly reflective edges. The Kern-Bolex 50mm f1.3 is the worst, and the Super Cinephor 4.75 inch f1.9 is close behind, where the Astro-Kino 65mm f1.5 fares a bit better.
I think I have found a possible solution to adding aperture control to projection lenses. I have tried it today on the Super Cinephor 4.75 inch f1.9 lens with pretty good results. What I found was a disc like aperture that fits inside a 52mm filter ring. It can sit between two 52mm filters. The problem is the aperture control is vertical, which means I can not change it unless I unmount the lens. I am working making the aperture control arm work horizontally, from the outside of the filters. This will only work with long lenses, unfortunately.