Quote Originally Posted by ReallyBigCameras View Post

It's well documented that the 450mm Nikkor M covers a LOT more than the published specs. I'm using one on 14x17 and have plenty of coverage. I don't have anything bigger to try it on, but the image circle needed for 12x20 isn't much bigger than for 14x17. I believe if you search the archives here and on the large format forum you'll find testimonials from several photographers who have successfully used the 450mm Nikkor M on 12x20.

Kerry Thalmann
Really Big Cameras
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.

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.

Sandy King