Extinction difference map obtained by subtracting the extinction map of RC1 from that of RC2 (top panel), along with the corresponding uncertainty map (bottom panel). The colour bars indicate the extinction values for each pixel and their associated uncertainties. Empty pixels correspond to regions with an insufficient number of stars to compute a value. The position of the supermassive black hole, Sgr A*, is marked with a black star in each panel, and the map sizes are indicated.