= Solution
<Fresnel diffraction> retains quadratic aperture-dependent propagation <phases> and generally depends on both aperture and screen distance. <Fraunhofer diffraction> neglects those <phases> and gives the <Fourier transform> of the aperture in angle space, either sufficiently far away or in a suitable lens's focal plane.
The calculations below use the \b[Fraunhofer, <paraxial approximation>]. For an overall aperture scale $D\sim1000\lambda$, free propagation requires $L\gg D^2/\lambda\sim10^6\lambda$. The printed $L\gg1000\lambda$ alone only makes the separation small relative to distance; it is not by itself the full far-field condition.
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