Peak magnification μ_peak as a function of source redshift z_S for different H II region sizes (diameters of 2R_S = 1, 10, and 100 pc), assuming perfect alignment between the source and the lens. Different line styles and grayscales represent various BH masses and distances, following the same convention as in Figure 1. Compact H II regions (1 pc) exhibit magnifications ≳10 for nearly all lens configurations, while more extended H II regions (10–100 pc) achieve comparable magnifications only for the most massive and nearby BHs.