Experimental radial profile comparison of dark holes obtained on the test bench without square zone (directly using the estimator described in Eq. (36)) (red, solid) and with square zones of different side lengths: K_Sq = 26.4λ/D_L (blue, dotted), K_Sq = 24.5λ/D_L (green, dashed) and K_Sq = 20.8λ/D_L (black, dot-dashed). These phase-only corrections were achieved with a γ = 16 reference pupil. The intensities are normalized by the highest value of the PSF obtained without coronagraphic mask.