Approximately 1600 pores were sampled in the analyzed area. Irregularly-shaped pores are clearly observed in Figure ,b and Video S1. We therefore quantify average pore size and size distribution using mean Feret diameters (i.e., an average between the longest and shortest dimensions of a given pore). Figure plots a histogram of mean Feret pore diameters that demonstrate dp to be ~128±80 nm with a lognormal size distribution. Figure shows size histograms for the minimum and maximum Feret pore diameters (dp,min=88±56 nm; dp,max=163±105 nm). Mean pore dimensions are between ~/4 and ~/15 (~eff/2 and ~eff/8 for n=2) in for the MAPbBr3 transmission window (~535 to ~2000 nm), explaining the more significant scattering effects observed near the perovskite band edge versus longer wavelength (see Figure and Figure ). While it is clear that reducing dp and P will enhance transparency, the exact values of each parameter necessary to optimize optical transparency for perovskite ceramics are not well understood. We thus model the effects of P and dp on optical transparency through a combination of Mie theory to estimate pore scattering efficiencies, cross-sections, and extinction coefficients shows spectra modelled via Mie theory (dashed-dotted black/blue lines) as a function of dp and P, respectively. In each case, the l=0.989 MAPbBr3 ceramic data (red line/shaded regions) and theoretical maximum transmission (dotted black lines) are provided for reference.