Left: Comparison between the SDSS photometric redshift and the spectroscopic one for targets located within R ≤ r₂₀₀ in the Perseus cluster with an r-band magnitude r ≲ 17.7. Right: Comparison between the photometric redshifts derived with Phosphoros and the spectroscopic ones for targets located within the Euclid field of the Perseus cluster (R ≤ 0.25 r₂₀₀). The vertical black dotted line shows the adopted limit in spectroscopic redshift used for identifying Perseus members [z_spec ≲ 0.03, corresponding to V_c + 3.5 σ_c = (5258 + 3.5 × 1040) km s⁻¹]. The green dashed line shows the limit in photometric redshift to identify potential cluster candidates [z_phot,SDSs ≲ 0.1, left; z_phot ≲ 0.1, right]. The upper and right histograms show the spectroscopic and photometric redshift distribution, respectively, for all galaxies and for those objects classified as cluster members using their spectroscopic redshift (z_spec ≲ 0.03, red).