Same as Fig. 10 but with S(3839) measured following the classical definition used by Campbell et al. (2012), Norris & Freeman (1983), and Smith & Norris (1982) for a fair comparison with their results on NGC 1851, M 22, and NGC 3201, respectively.The KDE bandwith is the average uncertainty of each dataset, i.e., σ_NGC1851 = 0.035, σ_M22 = 0.07, and σ_NGC3201 = 0.05, respectively. The KDE bandwith for our dataset is 0.031. δS(3839) was calculated for all samples following the same strategy as done in Fig. 4.