Relative attenuation of the peak intensity induced by the derivative filtering as a function of the scale of the structure. The diagonal directions have been divided by to take the longer distance along the diagonals with respect to the normal axis into account. For scales longer than ~6 pixels, the damping increases as a power -law function with an exponent −2. The dark grey dashed line refers to the typical size in pixels of the PSF in Hi-GAL maps.