Simulation of a Crab-like spectrum with the EPIC pn detector on XMM-Newton and the planned Athena-WFI instrument for a selection of read-out modes with different qualification to study bright sources. Panel a: fraction of piled up events in all detected events for increasing source flux. Panel b: index of a power law fit to the simulated spectra, showing the effect of spectral distortion with increasing source flux depending on the detector and read-out mode. Panel c: obtained power-law index plotted for the determined pile-up fraction, revealing a similar and generic behavior, largely independent of the detector.