The flux distribution in the difference images (original 500 μm image – convolved cirrus image, e.g. Fig. 2 panel f)) for 8 iterations from 1 to 20 in the ℓ = 30° field. In each iteration, the negative flux distribution was mirrored about 0 and a Gaussian was fit to the distribution to determine the characteristic fluctuations so that a source identification cutoff (of 4.25σ) could be applied. Plotted here are the full distributions, not the mirrored distributions used to fit the Gaussian. As we iterate, points in the negative end are transferred to the positive end of the distribution as flux is restored in the negative bowls around bright sources. The Gaussian fit to the distribution for the final iteration (16) is shown as the black curve.