Agreed that lens design has a practical effect as does the subject being imaged. I think the only thing that the Rockwell tables are trying to convey is the diffraction limited performance. The point being that even though a Tessar does get better corner to corner at f/22, that because of diffraction, some resolution is sacrificed in the center as a trade off for the improved corner resolution. No free lunch in other words. In practice, it just doesn't matter all that much for most LF shooting. It does matter for small formats, and shooting 35mm film at f/16 is just not a great idea if you plan on enlarging a lot.

Quote Originally Posted by Ian Grant View Post
It's not quite as simple as Ken Rockwell states. It depends on the lens focal lenght type of design etc.

LF Tessar's, and similar designs like Xenar's of around 135mm to 150mm etc are generally bests at f22 and in fact give poor edge/corner sharpness until stopped down to f16.

However more modern 6 element designs are far better optimised and will give better results at wider apertures, this is where depth of field tables, calculators etc become more useful.