Top panel: same as Fig. 7 but zooming in at the arriving photon energy flux. The volume-averaged magnetic field strength inside the magnetised region is assumed to be nG. Bottom panel: same as on the top panel but for 1ES 1218+304. The injected luminosity normalisation is L₀ = 8 × 10⁴⁵ erg s^-1 and the volume-averaged magnetic field strength inside the magnetised region is assumed to be nG.