I owned a 19" Artar some years ago and used it on an 8x10. I'm curious to hear if it covers 12x20 at infinity. I would imagine a 24" Artar would be a better choice for 12x20 or better yet a 30". My Korona 12x20 is limited by bellows (24") I use a 21 1/4" Kodak Ektanon which actually has more coverage than the 24" Artar ( and they usually come cheap). Also my 16 1/2" Dagor works beautifully on this camera and easily covers. Welcome to the world of ULF.