Two-dimensional representation of the N-PDFs of contaminated clouds after applying the constant screen correction as a function of the ratio between the contamination strength N_contam and the typical cloud column density N_peak. The width of the cloud N-PDF was assumed to be σ_η,cloud = 0.5 and the width of the contamination σ_η,cont = 0.15, using some typical values for the clouds in this paper. The N-PDFs are represented through colors showing the logarithm.