Comparison of the CMDs of the circular annuli around Cluster 1 and three nearby control fields indicated in the upper right panel. In this map the  ×  sign indicates the center of the galaxy. The plotted points correspond to sources having crowd <1.0. In the CMDs, sources with crowd <0.3 are marked by an empty circle concentric to the filled one. An isochrone providing a reasonable fit to the observed CMD is also over-plotted to the C1 CMD (thick red line). A selection box for the BL population is superimposed to each CMD.