Equivalent width ratios for the 12 Cu I lines analysed in this paper, calculated for five different stellar atmosphere models. The left panel is the LTE versus non-LTE EW ratios based on our recommended LCAO + Free non-LTE model. The right panel is the non-LTE with the LCAO + Free model versus non-LTE with the B21 model EW ratios. In both panels, the line at 809.3 nm for the metal-poor dwarf is not shown because the EW is too small.