Examples of SHWFS images and feature images with the same aberration. Panels d–f show the feature images of corresponding SHWFS images, panels a–c, respectively. In order to compare these three feature images more clearly, the sub-aperture feature images boxed in red in panel d are shown in the first row of panel g, respectively. The second and third rows in panel g show the corresponding sub-aperture feature images in panels e and f, respectively.