Improvements factors when using PCA background subtraction instead of mean background subtraction for mean retrieval (left panel) and RMS (right panel). Each point represents the ratio of the value obtained for PCA background subtraction and mean background subtraction. The background annulus inner radius is always one pixel larger than the mask radius. For each dataset, with its given mask and annulus size, we rejected up to 5 outliers which are here represented in red. These outliers are determined with respect to their RMS. The solid line represents the geometric mean of the improvement factors of individual nods, without the outliers.