JUNGFRAU is a charge integrating hybrid silicon pixel detector primarily designed to equip SwissFEL, the free electron laser at the Paul Scherrer Institut. The charge integrating architecture ensures responsiveness to the brilliant, short (~ 10 fs) pulses of photons, while three dynamically switching gains ensure single photon sensitivity above 2 keV and a high dynamic range of 10⁴ 12 keV photons. These proceedings detail the first full dynamic range scan of the JUNGFRAU performed at an XFEL in controlled conditions. A robust and accurate intensity measurement is achieved by counting the number of photons detected in an attenuated area of the detector. The scan provides a fascinating study into the response as a function of intensity, and allows the accuracy of the standard correction procedure to be quantified. The calibration constants, routinely calculated at PSI, and the pedestal offsets, typically measured by forced switching in dark conditions, are shown to be good. Small differences between results from the two methods lead to ideas and proposals for future measurements.