[ic-racer]

Large format lenses are normally designed and optimised for use at f22, they are not diffraction limited to f16, and are still very usable at f32 and in many cases f45. You only need to read data from Zeiss, Schneider & Rodenstock etc and use lenses at these apertures and make large prints to see this statement isn't true.

You can't 'design' a lens to have any specific diffraction characteristic. It a physical function of aperture size. Its simple, the smaller the aperture, the more the diffraction (or the larger the bullseyes). Its physics of light, not design of the lens.