Noise in residual images as a function of angular separations. Compared to standard HRSDI, modified HRSDI built multiple reference spectra annularly (see Sect. 4.2.1 for details) and applied extra wavelength calibration (see Sect. 4.2.2 for details). Additional median filters were applied on the residual images processed by modified HRSDI. No PCA was used to avoid reducing planet emission caused by aggressive PCA.