Variance in the PCA-cleaned cubes as a function of N_fg. The solid blue line corresponds to a PCA cleaning applied to the original footprint OF that, if cropped a-posteriori on the smaller CF, corresponds to the variance displayed by the solid orange line. The solid green line corresponds to PCA performed directly on the CF. We compare these results with a weighted PCAw with dotted lines, in the OF case (red), OF-later-cropped (violet) and CF (brown). The horizontal stripes mark the estimated noise level of the OF (pink) and CF (grey) cubes. These results do not change for an SVD analysis.