Profiles of three Ca lines computed for a giant star with [Ca / H]  ≈  − 2.5 with LTE (thin blue line) and NLTE (thick red line) hypotheses. The wavelengths are given in Å. a) The NLTE profile of the Ca I resonance line is narrower in the wings and deeper in the core. b) In a Ca I subordinate line, for the same abundance of calcium the equivalent width computed under the NLTE hypothesis is slightly smaller. c) The NLTE correction is important for the strong IR Ca II line (note that the scale in wavelength is different for this line), but the wings are not affected and a reliable calcium abundance can be deduced from these wings via LTE analysis.