How can I find or make a Neutral density filter using this 39mm Bayonet ring?
I am working with a 16mm Nikkor Fisheye, which uses these rear filters, and I would like to use my Wratten ND gelatin filter with this lens. Can I purchase a gel filter holder, 39mm bayonet, of some kind from Nikon? The 10.5mm Nikkor Fisheye has a holder on the rear for gelatin filters, but I can't seem to find an equivalent system with the 16mm lens. I have the gelatin filter to cut, what can I do?