Accuracy of the flux determination. Top panel: for the same simulation described in Fig. 11, the histograms show the results for three different fitting methods: regular grid 100 × 100 pixels (standard tfit approach), regular grid 200 × 200, single fit on the whole image. The small boxes show the extended wings of the histograms, magnified for better viewing. The accuracy increases by enlarging the cells and, reaches the best result with the single fit on the whole image. Bottom panel: the histogram shows the relative measured flux difference between the single fit on the whole image and the cells-on-objects method. Differences above 1% are very rare.