Negligible impact of the extended PSF on physical parameters of very extended sources. Top-left panel: I_E = 14 elliptical galaxy with a full extension less than that of the extended PSF (r = 300ʺ). Bottom-left panel: I_E = 9 galaxy (NGC 1553) larger than the extended PSF. Right panels: relative variation of the flux redistribution after convolution with the extended PSF. The effect is at the sub-percent level and does not impact the derived physical properties such as their photometry or morphology. The colour intensity is in logarithmic scale in all four panels (-3.0 indicates a 10^–3 ratio, or 0.1%).