“…In principle, " 2 could have little or nothing to do with relative L-and M-cone numbers but instead reflect the relative L-and M-cone contrast gains. This view is doubtful, however, given that L:M-cone ratio estimates derived from luminous efficiency functions correlate with estimates derived in the same subjects using other methods (e.g., Albrecht, Jägle, Hood, & Sharpe, 2002;Brainard et al, 2000;Kremers et al, 2000;Lutze et al, 1990;Rushton & Baker, 1964;Sharpe, de Luca, Hansen, Jägle, & Gegenfurtner, 2006;Vimal et al, 1989;Wesner, Pokorny, Shevell, & Smith, 1991). Nevertheless, any claims that luminous efficiency can be used to derive cone numerosity directly should be treated with extreme caution.…”