Evolution of dimming area and brightness in the September 6, 2011, event. The data from STEREO, having a higher cadence, are smoothed. (a) GOES 1−8 Å soft X-ray flux. (b) Instantaneous dimming area evolution over time for SDO/AIA 211 Å data (blue curve) and STEREO/EUVI-A 195 Å data (red curve). (c) Instantaneous dimming brightness evolution over time. Showing the comparison between SDO/AIA (blue curve) vs STEREO/EUVI-A (red curve). (d) Instantaneous brightness evolution within the fixed mask. The dashed horizontal line marks the pre-event brightness level.