Age–metallicity distribution obtained from the composite CMD of synthetic clusters (sets with single metallicity sequence). Left panels: Result from the mock with the small number of stars. Right panels: Results from the mock with intermediate number of stars. The results for the XL bins (upper panels) and S bins (lower panels) are shown. The two horizontal lines mark the metallicity range of the input population, and vertical lines indicate the input ages. Best-fit ellipses with 1σ axes are overlaid.