Examples of SEDs of post-AGB binaries. Top panel: IRAS 08544-4431. Lower panel: IRAS 18281+2149 (AC Her). Labels showthe sources of photometric data points (see also Sect. 4). We used these well-studied objects as prototypes for objects where the inner rim of the disk starts at sublimation radius (top panel) and objects where this inner rim is further out (bottom panel). The wavelength where the dust excess starts to appear is used as observational signature.