I see a lot of old lenses sold on ebay, some interesting things, for 16 and 35mm cameras. C-mount, exacta mount. etc. 90mm f/1.8 etc. and some 10:1 zooms. are there any guides, charts etc, that lists what types of mounts are convertible, what systems let converted lenses work. I know there's stuff like that for medium format shooters, who used to convert russian lenses to mamiya and bronica, take old large format soft focus lenses to fit on hassleblads.