Hess diagrams (displayed using ACS filters) for ESO318-20. The density values are listed along the colorbars. Panel a) Data; the reported densities are in units of number of stars per bin (with a binsize of 0.05 mag in color times 0.10 mag in magnitude). Panel b) Best-fit synthetic model, with a reverse color scale with respect to the data to facilitate comparison; units are number of stars per bin. Panel c) Difference between data and best-fit model; units are number of stars per bin. Panel d) Difference between data and best-fit model, weighted by the Poisson errors; units are proportional to the square root of the number of stars per bin.