Illustration of the Direct method. The vertical dark grey band is the 2997   GHz IRAS band, and the 3 clear-grey bands are the 3 Planck-HFI bands (857   GHz, 545   GHz and 353   GHz). The red line represents the spectrum of the warm background cirrus, on which is added the spectrum of point sources at various temperatures: 7K, 14K, 20K and 30K. In the Direct method, the detection is performed at each frequency separately, and the method deals with all types of sources above the background level.