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.
Originally Posted by fotoman
This goes back to the Tessar design where edges and corners aren't sharp until f22, which is the recommended aperture given by Carl Zeiss & later Doctor Optic. Lenses like the late production f5.6 150mm Xenar stop down to f64 annd are excellent at f32. Sometimes the effects of diffraction are over-hyped and the very small decrease in image sharpness in the centre has to be traded off against an increase at the edges and also far greater DOF. In most cases it's the last marked aperture that begins to suffer diffraction, and you'd have difficulty seeing any drop in quality in a print, but of course it can be measured on an optical bench, or by examining negatives of test charts with a microscope.