Is there any site which shows a list of the fitments lenses can have? Mine has a 39mm thread and I'm in need of a lens to do 120 film (so around the 80mm mark) but looking on eBay most don't list what fitment they have. They'll just list "nikon" or "rokkor" and say nothing else. I assume if you're in the know it'll come easy to you and be obvious. But not to me, yet.