I tried the landscape lens from his book for an 8x10. I designed the lens to be about 1.5 the diagonal of the format to get decent coverage. Wide open it was about f7 (focal length of the lens system/lens dia....not sure whether this is strictly correct). The coverage was adequate at f7 with lots of pleasing (to my eye) light fall off. I also used it with an f64 stop (calculated from greene's book). The F64 made a fairly pleasing contact print. I have the images and the camera on my flickr page at fotofish. I purchased my lens elements from Anchor Surplus. They have a huge selection.