Comparison between stellar parameters obtained in the optical and the infrared. Upper left panel: effective temperature. The dashed lines represent ±1000 K; upper right panel: logarithmic gravity (±0.1 dex). Star #9 has been slightly shifted from its value in Table 6; lower left panel: log Q (±0.2 dex); lower right panel: Y_He(±0.03), and stars #10 and 8 have been slightly displaced from their values in Table 6. Numbers indicate the stars as listed in Table 1.