Influence of the increase of the emission-line fluxes on the oxygen abundances obtained through different calibrations. Panel a: difference between oxygen abundances in H II regions in nearby galaxies obtained with the original R₂ = R_2,0 emission lineand with the emission line R₂ = 1.3R_2,0 increased by a factor of 1.3. The symbols represent the mean values of the abundance differences for objects in bins of 0.05 dex in (O/H). The bars (comparable with the symbol size) denote the mean values of the scatter of the differences in the bins. Panel b: influence of the increase of the R₂ and N₂ emission-line fluxes on the oxygen abundances (O/H)_R. Panel c: influence of the increase of the N₂ and S₂ emission-line fluxes on the oxygen abundances (O/H)_S.