Top: the equivalent widths of Na i+Ca i versus CO[2 − 0]+CO[4 − 2] as an indicator of T_eff and log g for dwarf (open circles) and giant (filled circles) template spectra from the IRTF spectral library. Spectral types are color-coded according to the legend in the upper left. The red and blue lines guide the eye to the two relations. Bottom: the same plot including the derived dwarf and giant relations (red and blue curve) as in the top panel, overplot with the ONC target components. Open symbols show targetsted with high veiling r_K > 0.2, filled symbols r_K < 0.2. Two targets, TCC 15B and [AD95] 2380B, are off bounds at high W_λ(Na i+Ca i).