Metallicity of M dwarfs - II. A comparative study of photometric metallicity scales V. Neves, X. Bonfils, N. C. Santos, X. Delfosse, T. Forveille, F. Allard, C. Natário, C. S. Fernandes and S. Udry A&A, 538 (2012) A25 Published online: 27 January 2012 DOI: 10.1051/0004-6361/201118115