Correlation of the [Ca/H] results calculated for a sample of 61 591 stars, using different spectral regions containing Ca lines (neutral and/or ionized), compared with the estimation obtained by fitting all of the selected lines together. The CaII lines are the most sensitive to changes in the abundance of calcium, in particular the Ca HK doublet, hence they are the primary features used. Of the neutral lines, the CaI line at 4226.73 Å is the most relevant.