Power-law fits to the ridge-line in N(θ_r, σ_ν)—defined as the location of maximum σ_ν for every fixed N—for four different observing frequencies; this ridge-line can be seen as the turnover in the contours in Figure 7. Configurations of (θ_r, σ_ν) that fall below and to the right of the ridge-line can most effectively increase N by improving angular resolution (i.e., by decreasing θ_r), while configurations that fall above and to the right of the ridge-line can increase N by improving sensitivity (decreasing σ_ν) or by increasing θ_r. For reference, we mark the approximate specifications of the EHT (i.e., θ_r = 20 μas, σ_ν between 1 mJy and 0.5 Jy) by a shaded gray region.