If the G Claron will cover 12x20, then so should the Schneider Symmar 360mm f/6.8 or f/5.6, which I believe give more coverage than the G Claron. They are extremely reasonably priced in a barrel (SINAR DB or DBM mount), and give top-notch performance from what I can see, even on 4x5 (which is what I usually use it for). I got mine (f/6.8 model in DB mount) for under $300 shipped with caps in outstanding condition. LF prices are INSANE!!! This is a lens that I would used to have needed to save up for for YEARS to afford, and I got it for what amounts to allowance money in the grand scheme of things.