I have used the 450mm Nikkor M on 20X24. You must stop down to f/64 or more for decent performance on the edges, and even then it is only good enough for contact printing. But the circle of illumination is very large and even allows a bit of movement on 20X24.
Originally Posted by ReallyBigCameras
This has got to be one of the best lenses every for ULF. When I bought the 450mm Nikkor M I had a 19" Dagor, coated. The Nikkor outperformed it in every way, including useful coverage on the edges. I sold the 19" Dagor and never looked back.