Supplementary Figure 3: TRABI photon count estimate as a function of aperture size and PSF model.

(A) Ratio of the estimated photon count by TRABI and simulated number of signal photons captured at the camera as a function of aperture diameter for two PSF models. TRABI aperture diameter (d) of 2 × 1.86 × FWHM (FWHM = 214.5 nm) as suggested in Franke et al.¹ is indicated. For this aperture size, we find TRABI to estimate 92% and 85% of the total number of photons according to the low-NA scalar Airy PSF model and the high-NA vectorial PSF model, respectively. The fraction of the total energy contained within an aperture of the prescribed radii in the Airy PSF model (PSF_Airy(ρ) = [2J₁(D)/(D)]² where D = 2πρ(NA/λ); FWHM = 0.514(λ/NA)) follows the analytically derived formula by Born & Wolf (ref. 4 in the Supplementary Methods reference list; Chapter 8; Fig. 8.13), in contrast to the 100% reported by Franke et al.¹ in their supplement. The PSF simulations were performed with 2,500 signal photons and no background photons and a pixel size of 1 nm (to exclude quantization effects). Otherwise, the simulation parameters were the same as the experimental parameters. (B-C) Characterization of the Airy and vectorial PSFs as a function of the radial position in a linear and log scale, respectively, showing the long tail of the PSF.