Differential intensity measured on simulated images with tip-tilt applied along the x axis. The blue solid line corresponds to the flux integrated in the inner area only, while the red dashed line corresponds to the flux integrated in the outer area of the image. The light blue dotted and red dash-dotted lines are the linear approximations for the inner and outer measurements, respectively, that are valid in the small tip-tilt regime (i.e., <0.15 λ/D_L and <0.5 λ/D_L, respectively).