Comparing independent segment WFE tolerances for different levels of differential target contrasts, calculated from the experimental PASTIS matrix, M^exp. The tolerances for Δc_t = 5 × 10⁻⁷ and Δc_t = 3 × 10⁻⁷ have been validated experimentally in the current performance regime on HiCAT. The other lines describe predicted requirement limits on the segmented mirror for deeper contrast levels. These curves isolate the influence of segmented mirror drifts from other system components that influence the contrast. The curves appear top to bottom in the same sequence as in the figure legend.