Left: geometry of the IrisAO segmented DM on HiCAT and the segment numbering used in this paper, in the entrance pupil. The 37 segments are numbered, from 0 for the center segment to 36 in the outer ring. In the exit pupil, most of the outer ring segments are obscured by the LS (see Fig. 4). Middle: experimental PASTIS matrix for HiCAT as measured on the testbed. Each entry represents the differential contrast contribution of each aberrated segment pair. The matrix is symmetric, and its diagonal shows the impact on the contrast by the individual segments. Right: simulated PASTIS matrix for HiCAT, without any WFE or noise in the optical system. This matrix shows the idealized contrast contributions from each segment pair in a perfect system.