Completeness function in luminosity of the H II regions detected by HIIPHOT for galaxies belonging to the different substructures of the cluster located at 15.8 (cluster B, C; magenta), 16.5 (cluster A, LVC; blue), 23 (W′ cloud; green), and 32 Mpc (W and M clouds; red), respectively. The vertical dashed line shows the limit in Hα luminosity adopted to define a complete sample where statistical properties are derived. The black arrows show how the position of a limiting Hα luminosity L(Hα) = 10³⁷ erg s⁻¹ should be shifted for a dust attenuation of A(Hα) = 1 mag or a [N II] contamination of [N II]/Hα = 0.5 (for reference, the measured values for NGC 4321 used for this test are A(Hα) = 0.85 mag and [N II]/Hα = 0.48).