Log([S II]/Hα) as a function of logarithm Hα surface brightness for all pixels in each galaxy. The red solid line is the fitted correlation for each galaxy, with slope and intercept values given in the legend of each panel. The black solid line is representative of the DIG relation, as measured between 0.40 R_max (maximum radial coverage) and 0.60 R_max for each galaxy from Belfiore et al. (2022). The gray area indicates the 3σ range of this relation. SNRs typically lie above the fitted lines and show a looping structure toward the upper right. The horizontal black dashed line indicates the typical value of [S II]/Hα = 0.4 used to select SNRs. Many low Hα surface brightness pixels associated with the DIG have [S II]/Hα ≥ 0.4.