Photometry results of the extraction of the real MCXC clusters using the proposed X-ray matched filter and assuming the position and size of the clusters are known. The six panels are analogous to those in Fig. 1, but comparing the extracted L₅₀₀ with the published L₅₀₀. Individual measurements in panels a), c), d), e), and f) are shown as black and blue dots: the black dots correspond to clusters originally detected in RASS, the blue dots to serendipitous clusters. Panel b) shows three histograms that correspond to the RASS clusters (black), the serendipitous clusters (blue), and the complete MCXC sample (red).