Dimming detection. First row: Expansion of the dimming area, A(t) (top panel) and its time derivative, dA/dt (bottom panel) over 4 hours. Second row: Cumulative timing map of the dimming extraction, colour-coded in minutes from 10:37 UT using STEREO-A 195 Å logarithmic base ratio images. Third row: STEREO-A 195 Å base-difference image together with the boundary of the identified dimming region (red) at the end of the impulsive phase (11:50:00 UT). Point C is the filament source, and points A and B mark the largest extent of the north and south dimming.