Location of the cool stars identified in the observed Lupus 3 field (filled dots) in the (I_C − J,J) and (J − K_S),(I_C − J) diagrams. The location of such cool objects above the main band defined by the photospheres of hotter stars reddened by various amounts in the right hand diagram is clear. Their position in the (I_C − J,J) lies in all cases well below the 5 Myr isochrone from Chabrier et al. (2000), indicating that these objects are not members of the Lupus 3 star-forming region. For comparison, the location of known members of Lupus 3 (Sect. 5.2) is marked with empty circles in the color–magnitude diagram on the left. The dotted line in the (I_C − J,J) diagram indicates an extinction vector corresponding to A_V = 5 mag.