Comparison of input and output flux densities. Upper and middle panels: ln(S_out/S_in) versus NPSNR distribution contours ([68, 95, 99]%). In the upper panel the field and patch are 513 × 513 and 129 × 129 pixels, respectively, and in the middle 129 × 129 and 33 × 33. For both cases a source was directly injected in the central pixel of the patch, but always with a small random shift from the pixel centre. Lower panel: “normalized error” =(S_out − S_in)/ΔS distribution contours for the small patches. The horizontal lines in the bottom panel, are the ±3 σ boundaries.