Frame differences of the ramps for the different calibration methods in the PSF centre ((x, y) = (415 940)), and the PSF wings ((x, y) = (414 940) and (x, y) = (416 940)), in band 1A (left). To better visualise the deviation from perfect linearity, we show the subsequent frame difference (DN_i+1 − DN_i). A perfectly linear ramp should be horizontal and straight. Note that the ramps in the panel on the left are cut at the saturation point. We also show the frame differences of the uncorrected ramps 3 pixels from the PSF centre (right).