[C/Fe] abundance ratios as a function of the stellar metallicity. The panels show the carbon abundances derived from the spectral synthesis (circles) of two molecular bands (5128 and 5165 Å) and one atomic line (5380.3 Å) and from the equivalent widths (squares) of two atomic lines (5052.2 and 5380.3 Å). Stars cooler than 5000 K for 5052.2 Å (EW) and than 5200 K for 5380.3 Å (EW) are not plotted (see the discussion in Appendix A).