Hα theoretical profiles for models with log g = 4, [Fe/H] =  −3 (solid lines) and log g = 4, [Fe/H] =  −2.5 (dot-dashed lines) have been fitted with the same procedure used for the program stars, but using a log g = 3.5 grid (red lines with filled circles) and a log g = 4.5 grid (blue lines with open diamonds). Here we plot the temperature difference (T_eff(log g = 3.5/4.5) – T_eff(log g = 4.0)), against the “real” effective temperature of the profile. The upper panel shows BA profiles, the middle panel ALI profiles, and lower panel 3D profiles. The gray shaded areas indicates the temperature ranges for the program stars in each T_eff scale.