Comparison of theoretical ISs considering linear (left panel) and quadratic (right panel) relations for Z = 0.008 presented in De Somma et al. (2022; red, blue, and green) and our empirical IS (black) in an HRD. Different line styles represent different cases of the luminosity adjustment (increase) applied by the authors to their canonical model. Different colors represent different efficiencies of superadiabatic convection α_ml. Shaded areas represent one sigma errors on the edges.