Ionization balance of Fe for all MP SAGA stars for which log g has been derived using the standard spectroscopic method (left), and theoretical isochrones or stellar parallaxes for all MP stars (middle), and only stars with [Fe/H]_LTE > −2.5 (right). The shaded histograms are the original LTE distributions of all MP stars (grey) and of dwarf stars (cyan; T_eff = [5000, 6500], log g = [4, 4.5]). Red and blue show the corresponding distributions after applying 1D NLTE corrections for all stars (Bergemann et al. 2012c) and 3D NLTE corrections for the dwarf sample (Amarsi et al. 2022), respectively.