Panel a) selected field dwarf stars from the sample of CAS11 plotted in the unreddened m₁,  y − H plane (Ns = 488, filled dots). Stars selected for σ_J,H,K <  0.03 mag are marked with red crosses (Ns = 185). Panel b) difference between photometric and spectroscopic metallicities, plotted versus the spectroscopic metallicity for the 488 field dwarfs. Photometric metallicities are based on the m₁,   y − H MIC relation. Panel c) difference between photometric metallicities based on our m₁,   y − H MIC relation and photometric metallicities by CAS11 plotted versus spectroscopic metallicity. Panel d) photometric metallicity distributions for the 488 dwarfs (black solid line) and for the selected 185 stars (red dotted) obtained with the m₁,   y − H MIC relation, compared to the photometric distribution by CAS11 (black dotted) and to the spectroscopic distribution (black dashed).