Image RMSE, δ, for ℓ2-magnitude, ℓ2-roughness, and ℓ2-TV reconstructions as a function of the number of views for the number of bins fixed at 512, and the data distance D(X f⃗, g⃗) constrained by ε = 10−5. The horizontal dashed line shows the level of the minimum gray-level contrast in the breast phantom. The labels SSC1, SSC3, and SSC4 are the sufficient-sampling conditions discussed in Section IV-A.