Annuli around measured sources (Sect. 2.6). The field of Fig. 2 is shown as the true intensities of the model sources at 350 μm convolved to a 17′′ resolution (left), the image of annuli of all detected sources (middle) slightly modified to highlight the annulus area around the source 244 from Fig. 14, and the product (right) to visuaize the actual observed intensities used to compute the flux uncertainties σ_iλ   P shown in Fig. 15. The corresponding footprint images ℱ_λ are presented in Fig. 15 and the observed image ℐ_λO is displayed in Fig. 18. The color coding in the left panel is a function of the square root of intensity, in the other panels it is a linear function of intensity in MJy/sr.