Panels a) and b) show the LOS magnetic field (in the observers frame) at τ_c = 0.95, for inversions made allowing for respectively 2 and 3 nodes for the LOS magnetic field, 2 nodes for the LOS velocity field and 3 nodes for the temperature. Panels c) and d) show the LOS magnetic field at τ_c = 0.09 and 0.01 with 3 nodes for the LOS magnetic field. Note the presence of opposite polarity field at τ_c = 0.95 in the penumbra, and the virtual absence of such opposite polarity field at smaller depths. The scaling of the magnetic field (in G) is according to the grayscale bar shown in panel a and is the same for panels a)−d). The FOV shown is 35 × 35′′. The plus symbols indicate the first and last pixels of the plots shown in Fig. 5. The long white arrow points in the direction of disk center, the shorter arrows to a pore discussed in Sect. 4.2.4.