Wilson depression of simulation run 1. Panel A: true Wilson depression, panel B: Wilson depression derived from the inversion. The black and white contours indicate the outer and the inner penumbral boundary. The dashed black contour shows the region that was used for defining z_W = 0 (distance of at least 7 Mm to the sunspot). Panel C: Wilson depression along a cut across the sunspot (marked by the dashed lines in panels A and B). Red: Wilson depression derived from synthetic observations, blue: true Wilson depression, black: true Wilson depression filtered in Fourier space to the same range in wavenumber as the derived solution from the inversion, for direct comparison with the red curve.