Experimental data: coronagraphic images recorded with SPHERE calibration unit in the H3 band before any NCPA compensation, after 2 iterations of PW+EFC in a FDH (center), and after 6 iterations of PW+EFC in a HDH (right). The sizes of the FDH and HDH are, respectively, 31λ/D × 31λ/D and 13λ/D × 31λ/D, 1λ/D being equal to ∼43 mas. The HDH starts at 2.85λ/D from the optical axis to get as close as possible from the FPM bottom edge whose radius is 92.5 mas or about 2.15λ/D. The aim is to ensure the stability in the PW+EFC closed loop. The edges of each DH are represented in white dashed lines. The images were normalized by the maximum of the off-axis PSF, recorded at the first iteration of the PW+EFC process.