Integral area-extinction relation for Orion A, i.e., the physical cloud area above a given extinction threshold (top panel), and the logarithmic derivative of this quantity (bottom panel). The solid black line shows the result for the entire field, while the solid gray line shows the region covered by Herschel alone. For comparison we also plot as a dashed gray line the same quantity as obtained from the 2MASS/Nicest extinction map and a simple S( > relation as a red line.