"Depth of field is insufficient"
So as I understand the Luminous Landscape article, lens have same DoF at same aperture, no matter what their focal length.
I tested different zoom lenses at same focal length and aperture for their DoF:
The sharpness in the middle and back is clearly different. But according Luminous Landscape, the DoF should be the same here also (same aperture also same focal length). What accounts for the different sharpness in background then?
I will find time the read the Zeiss pdf to see if it explain this. It's practically a book. But I saw DoF and Bokeh being talked about there. Maybe it explains.
DoF is what you perceive as sharp, but if you see even a slight amount of blur on the subject that subject is already off the DoF. The other issue is lens sharpness.