This aperture series look at performance of the Schneider Kreuznach LS 40-80mm f/4-5.6 at 80mm on a planar target at far distance. Key issues include sharpness across the frame and particularly peripheral forward field curvature and focus shift.
See also this same series shot with the Schneider Kreuznach LS 80mm f/2.8. Regrettably I did not shoot things as an A/B direct comparison, but conclusions about the relative performance can nonetheless be made.
Includes images up to full 150MP camera resolution (14204 X 10652) from f/5 through f/11 including 100 megapixel versions for perspective vs other medium format cameras, plus crops.