Triple convertible lens for 11x14 / 12x20?
At some point in the future, I will take the plunge to 11x14 / 12x20 ULF. I already have a Nikon M 450 f9 but am looking for a triple convertible lens with enough coverage for ample movements; something equivalent to my Wollensak 13-20-25" that I am using on my 8x10 at the moment. I presume the desired focal lengths would be in the range of ca. 18-23-30" (?). I would appreciate any helpful suggestions, offers, etc. I am not in a big rush (this is a long-term plan) but want to keep my eyes open.
Thanks & best wishes,