Example of the 3D masking process. The blue solid line represents the variations of the S/N across the wavelength dimension for the source A2744-3424 in the A1689 cube. The red points over-plotted represent the 2D resampling made on the S/N curve with ∼300 points. To each of these red points, a mask with the closest S/N value is associated. The short and long dashed black lines represent the S/N level for which a covering fraction of 1 (detected nowhere) and 0 (detected everywhere) are achieved, respectively. For all the points between these two lines, the associated masks have a covering fraction ranging from 1 to 0, meaning that the source is always detectable on some regions of the field.