Dereddened KLF (see text) for sources in the H − K_s colour interval corresponding to a reddening interval 3.2 <A_V< 7.8 (see text) from the mean locus (pseudo-sequence) of young stars (histogram), for K_s counterparts of X-ray sources (full squares), and for sources in the reddening interval 3.2 <A_V< 15 (open squares). All are obtained with the pseudo-sequence at 1.7 kpc and from the whole field. Error-bars are derived from Poisson statistics.