Hδ/Fe I λ4045 vs. Ca II (at solar metallicity) for both the empirical and synthetic libraries. Empirical stars are plotted with symbols, while the indices for the synthetic stars are plotted as lines. Both libraries have been further separated by gravity as shown in the figure legend. Notice that the empirical dwarfs have a flatter slope than the synthetic dwarfs as Hδ/Fe I λ4045 increases past 1.0.