Effective source density estimated from the effective number of source, Eq. (9), and the geometric area of the radial bins stacked in bins of cluster redshift (panels, lowest redshift left, higher redshift right) and of richness (color coding) as stars, for our background selection. Cluster members contaminating our background source sample leads to an increase of the effective source density toward the cluster center, which depends on both cluster richness and redshift. This signal needs to be determined, as cluster member contaminants are not sheared and dilute the shear estimator. Our model (lines) captures this trend well.