Ionization parameter mapping of two H II regions, from left to right: Hα, [S II]/[O III], VRI. The grayscale for the Hα maps shows high intensity in black, whereas the IPM maps feature high ratios in white. The region i97 (top row, 4.8″ × 5.8″) is optically thick, while i81 (bottom, 10.4″ × 11.8″) is apparently leaking ionizing radiation, a “blister” in the nomenclature of Pellegrini et al. (2012). A strange, [O III]-bright feature near the rim of i97 is indicated by an arrow (see text). The stars that are likely responsible for the ionization of the nebulae are visible as blue objects in the VRI images.