Accuracy of the flux determination in a simulation containing extended objects, overlapping priors, and SExtractor detection. Top: relative flux difference (f_meas − f_true) /f_true versus logarithm of the input flux f_true for a simulated image populated with extended sources (FWHM = 1.66′′). Symbols and colours are as in Fig. 9. The inner panel shows a magnification of the brighter end of the distribution. The outlier marked with the open black circle, ID = 720, is shown in the bottom panel: left to right, HRI (FWHM = 0.2′′), LRI, SExtractor segmentation map and “true” segmentation map. The green circles show the object detected via SExtractor, while the blue cross shows its “true” position. See text for more details.