On reflection, I think it is better to give the user all the info and let them decide on how to use this info. Thus I've up the issue of FOCUS to show all the blur info at once:
- The total blur criterion, as set in the ML menu, is the height of the bar;
- The blue shows the total blur at infinity, ie the RMS of defocus blur and diffraction blur;
- The yellow shows the diffraction blur component;
- The green area shows the defocus blur component: if this turns red it means the defocus blur is less than two sensor pixels.