Residuals of measured and true equivalent widths ΔEW for S/N of 30 pixel^-1 (top panel) and 10 pixel ^-1 (lower panel). Measurements which were already rejected within EWCODE are shown as red dots. Thick black points indicate the means of the respective EW bins. Red, gray and black error bars illustrate the theoretical and true rms scatters within the trust region (see text) and the error provided by EWCODE, respectively. The corresponding abundance for this particular synthesized transition (see text) for a given EW_true is indicated by the top axis.