Reconstruction errors for a single binary star with the main component centred on (0,0). Each point on the map shows the measurement of the quantity labelled in each panel when a single companion star is located at that position. The labels are in arcsecond. The first column on the left shows the effect for a PSF aligned along e₁ and a contrast of Δm = 0 between the main star and its companion. The next column is for the same PSF shape and orientation, but for a contrast of Δm = 1. The block of six graphs on the right is for the same two contrasts, but for a PSF aligned along e₂. The red line represents the orientation of the PSF. From top to bottom, the total ellipticity (star + companion) of the PSF, the relative error on the ellipticity due to the companion star, and the relative error on the size are shown.