The current method to calculate diffraction includes a magnification term, which, when coupled with the optical blur, has the impact of changing the HFD with focus.
This is considered 'confusing', as the magnification (f/(x-f), where f is focal length and x focus distance) impact on diffraction really does seriously impact non-macro photography; and an HFD doesn't have any meaning in macro photography.
Based on the above I propose we change the equation in focus.c, ie from:
const uint64_t diff = (244freqlens_info.aperture*(1+imag)/imag)/1000000; // Diffraction blur in microns
const uint64_t diff = (244freqlens_info.aperture/1000000; // Diffraction blur in microns
This will create a diffraction that is only dependent on aperture and will not vary as we vary focus.