Analysis of a small region including a strongly covarying group of sources. Upper left panel: one of the 100 realizations with different noise maps of the region. Upper right panel: true spatial position of all the sources in the region (the colour of the dots refer to the covariance index of the sources, as indicated in the colourbar, while their size is proportional to their true flux). Bottom left panel: relative deviation of measured flux from the true flux for each source in the region, as a function of their true magnitude (big dots show the average relative deviation, and their colours refer to their covariance index as in the previous panel; green squares show the nominal uncertainty given by t-phot, to be compared with the rms of the distribution of the 100 measurements (diamonds); small grey dots are the 100 measurements. The insets show magnifications of regions of interest). Bottom right panel: each dot shows the sum of the measured fluxes for each of the 100 realizations, and the average of this sum (red line) to be compared with the true sum (blue line), showing that an overall consistency is guaranteed by the method. See text for more details.