Left three panels: Hess diagrams for the simulated 5, 7, and 10 Gyr simple stellar populations at the distance of NGC 300. The highest density regions of the RC are marked by crosses. We note the gradual change of the RC magnitudes as a function of age. Right four panels: observed CMD of F4, F5, and F6 and its LF (filled histograms) overplotted with the model LFs (open histograms). The red curved line in the CMD represents the stellar isochrone for age = 10 Gyr and [Fe/H] = −1.6 in the Padova models. The probability (P) of the Kolmogorov–Smirnov test for the stars brighter than F814W = 26.5 and 27 mag are marked in the panels with LFs.