Histograms of the I_ν(850)/I_ν(1380) ratio for the two Hi-GAL and Cold Cores Herschel large programs, deduced from the Planck data at 5′ in black, and from the predictions at 37″ in green. Gaussian fits are overplotted, with the central values (µ) and the standard deviations (σ) given in each panel. The left and right y axes in each panel correspond to the number of pixels for the Planck data and prediction histograms. See Fig. A.4 for histograms of all the Herschel large programs described in Sect. 2.2.