Left panels: umbra Stokes I/I_QS and V/I_QS profiles reconstructed using the PCA deconvolution and maximum entropy methods. Right panels: umbra Stokes I/I_QS and V/I_QS profile as seen by GREGOR and the German VTT. The solid line represents the non-reconstructed data while the dotted line stands for the reconstructed data. The black line corresponds to the German VTT (simulated), red to the GREGOR telescope, and blue to the observed VTT profile (see text).