Top left: part of the region with high-order Balmer lines for the metal-poor giant, along with the observed spectrum of HD122563. Bottom left: the same at the top left panel, but for solar parameters, alongside the observed solar spectrum. Right: H _α in the metal-poor giant, along with the observed spectrum of HD122563. None of the codes correctly model the hydrogen lines in the metal-poor regime. Though SME is the closest to the observed high-order Balmer lines in the metal-poor regime, it predicts strong high-order Balmer lines in stars where they are not present. All synthetic spectra have been convolved to the observational resolution.