Distribution of S/N per pixel for the different HERMES wavelength bands (S/N per resolution element is about twice as high) for the final sample. The S/N for the green, red and IR channels are mainly in the range of 50–150, that is, above the nominal survey aim of S/N of 100 per resolution element in the green channel. The S/N in the blue channel is smaller, with typically 25–100. The mean values per band are 59/75/94/88. This indicates a smaller influence of the blue band in the parameter estimation with χ² minimisation explained in Sect. 3 and lower precision of element abundances measured within this channel.