Standard deviation of the fitted Gaussian 2D profile for the small bright-spot-like feature pointed to by the yellow arrow. This is done for NFH, FFP and NFP. For photon fluences below 2 per pixel, the curves are greatly influenced by uncertainties, but meaningful results start to appear at higher photon fluences (with outliers for FFP at nph = 35 and 200 per pixel removed). The results agree with the visual appearance of the reconstructions shown in Fig. 2, where features in FFP reconstructions appear sharper when using the Poisson cost function at low photon fluence.