Sample squared visibilities measured for FT (small circles colored by baseline) compared to those derived from SC differential amplitudes (black circles and their averages as large squares) for 3C 273 (left) and IRAS 09149−6206 (right). The FT data have been divided by the best-fitting zero-baseline visibility, so that V²(0) = 1. With this scaling, the two independent measurements are generally consistent.