Transfer function derived on the night of the observation of Arcturus. Panels a, b, and c show the transfer function measured at baselines B2–C1, C1–D0, and B2–D0, respectively, taking the best 20% of the frames in terms of the fringe S/N. In each panel, the transfer functions derived from five AMBER observations of the calibrator α Cen A (C1–C5 in Table 1) are plotted in black (C1), red (C2), green (C3), blue (C4), and light blue (C5). The transfer function was stable throughout the night, and the five curves therefore nearly overlap.