Flux ratio as a function of the effective temperature derived for the NaCo SDI filters (Fig. 1). F₁, F₂, and F₃ refer to the fluxes in the filters at 1.575, 1.600, and 1.625 μm, respectively. The theoretical relations are derived for a given age of 70 Myr, so the surface gravity of the object log  (g) is not constant. It increases from 3.75 to 4.75 for the plot range. We also consider the same photometric zeropoint for all the SDI filters.