CMD of stars in the cluster field (left), the comparison field (middle), and simulated stars (right). The continuous black lines are the MS fiducials and the locus of equal-mass binaries, while the loci of binaries with mass ratio q = 0.4, 0.6, and 0.8 are represented with dotted red lines (see text for more details). Upper and lower panels show the setup used to measure the fraction of binaries in the intervals 20.3 < m_F814W < 21.3 and 21.3 < m_F814W < 22.3 respectively.