Comparison of source densities for consecutive passbands. The individual panels show the ratio of source densities for two particular passbands (e.g. J and y in the topmost panel) evaluated with a 1′ Epanechnikov kernel. The colour scale indicates the gain (or loss) of the redder band over the bluer. Clearly, the JHK_S VISTA observations show overall the best sampling of sources in the region and even redder bands include more extincted sources in the cloud. Due to the small difference in the extinction between I₁ and I₂, the source density gain is negligible for I₂. The apparent large-scale pattern for the second and third panel from the top is caused by the variable completeness of the VISTA observations.