2D histogram of the dataset used in this paper in the T_eff vs log g plane. The log g-limit of 2.7 applied in this work is shown as a dashed black line. The solid black line represents the mean in bins of constant log g. Red and blue crosses mark the location of the 3D M3DIS models. The insets show the temperature distribution at the optical surface of the respective model with [Fe/H] = −5. To highlight the different physical scales involved, the blue square in the inset shows the size of the MS model. To estimate the dependence of 3D A(C) corrections on effective temperature, additional models are created at the locations highlighted with green crosses.