Panel a) selected field dwarf stars from the sample of AR10 plotted in the unreddened m₁,  y − H plane (Ns = 221, filled dots). Stars selected for σ_J,H,K <  0.03 mag are marked with red crosses (Ns = 96). Panel b) difference between photometric and spectroscopic metallicities, Δ [M/H]    = ( [M/H] _phot −  [M/H] _spec), plotted versus  [M/H] _spec for the 221 field dwarfs (filled dots). Photometric metallicities are based on the m₁,   y − H MIC relation. Panel c) photometric metallicity distribution for the 221 dwarfs obtained with the m₁,   y − H MIC relation (black solid line), compared to the same distribution but for the selected 96 stars (red dotted) and to the spectroscopic distribution (black dashed).