Locations of the chosen area boxes and comparison of their brightness behavior for September 6, 2011, event. Left panel: SDO/AIA 211 Å logarithmic base ratio images during the impulsive phase of the dimming. Four colored boxes of size 3 × 3 pixels in different dimming regions of interest are over-plotted. The reference box is located in a random quiet Sun region. Right panel: Intensity evolution of the boxes from the original AIA images (top) and LBR images (bottom). The dashed horizontal line marks the pre-event brightness level. The dashed vertical lines indicate the peak time of the two X-class and the one M-class flare.