Fig. 4.

a) Cumulative spatial distributions of noise estimates for different estimators without (${\hat{\sigma }}^{\mathbf{W}}$) and with (${\hat{\sigma }}^{\mathbf{Y}}$) signal perturbation. b,c) Spatial maps of noise for estimator EXP2 b) without and c) with signal perturbation. d,e) Rank estimates $\hat{R}$, given as a percentage of the number of volumes N, for estimators d) EXP2 and e) ours. All results correspond to the RAMSE-optimal aspect ratio $\hat{\gamma }=0.85$.