Two example magnification maps for image C of B 1555. In both cases, the fraction of microlenses is α = 0.2. The source sizes for line, IR, and radio emission are indicated as orange, green, and red circles, respectively. The top panel shows that when many BHs are contained in a very dense cluster, the magnification map is dominated by the features caused by the clusters themselves (notice the flocculent giant caustic). The magnification distribution in the lower panel, on the contrary, appears closer to that of a uniform lens population.