If so, I would like to ask a favour.
I wonder if you would mind measuring the inside diameter of the opening, without an adapter ring fitted.
I've just acquired a Samyang 14mm f2.8, and it doesn't have filter threads, so I'm looking at a DIY solution to use GND filters by attaching a cokin type holder to a spare lens cap.
When it stops raining I'll do some tests to see if vignetting will occur with my proposed holder.
Thanks in advance.