Surface brightness distributions of the individual spaxels of LIRGs and ULIRGs. For clarity, we only plot a random distribution of the 20% and 50% of the points for LIRGs and ULIRGs, respectively. The colour code indicates the A_V value of each spaxel, whereas the points with A_V < 0 are outlined with a black contour line. The increase in the extinction towards low surface brightness values is mainly due to the high uncertainties of the flux measurements, in particular in ULIRGs, where the highest A_V values correspond to the spaxels with the lower Brγ surface brightness.