Peak signal-to-noise ratio of the candidate solution of the specified FISTA iteration for the first major cycle of the low- and full-resolution steps, respectively. The full-resolution images were constructed with î_ℒ set as a low-pass filtered version of the ground-truth image. We observed slightly faster reconstruction speeds for low values of ℓ in the low-reconstruction step, but these configurations are significantly slower in the full-resolution step. It should be noted that although lower values of ℓ improve faster for the low-resolution step, they do not necessarily converge to a better result, as illustrated in the dataset Sgr B2.