Linearity of the ePix10k detector in low gain. Top panel: the intensity of five chosen pixels when varying the incoming X-ray intensity to show the deviation from a linear response at different intensities across the detector (indicated by the colored dots in the insert showing the intensity distribution of the scattering from water). The data from multiple acquired images were binned based on the average intensity on the detector. The solid black lines a,b,c represent selected intensities where the correction is evaluated in Fig. 6. Bottom panel: nonlinear residuals after subtracting the first-order polynomial fit around a chosen correction intensity ic. The residuals from each pixel have been offset for visibility.