CFHTLS W1 cluster subsample: spatial location of the 18 clusters of our CFHTLS W1 subsample (red crosses). The magenta dashed lines represents CFHTLS W1 fields. For each cluster, blue circles have radii of 0.5 × , 1 ×  and 2 × r₂₀₀. Gray areas represent masked regions for f_blue estimation and background estimation, due to image corruption (rectangles) or potential clusters at similar redshifts as those of our cluster subsample for each field (disks and sectors).