Fourier difference maps at 900 ps and three different pump-pulse energies using data processed in space group P21. q-weighted Fourier difference electron-density maps calculated between SFX light (Δt = 900 ps) data sets at different pump-laser energies and the dark data set ( − with E = 3.7 µJ (a, e, i), 7.5 µJ (b, f, j) and 11 µJ (c, d, g, h, k, l) at 2.2 Å resolution. Maps are contoured at +3.5 r.m.s.d. (green) and −3.5 r.m.s.d. (red). The SFX dark-state model (PDB entry 6zh7) of monomer A is overlaid in (a)–(d) and that of monomer B in (e)–(l), with FAD in yellow, the fatty-acid substrate in green and the protein in light gray. The maps were calculated with 68 421 dark images and with 18 704 light images in (a), (c), (e), (f), (i) and (k) (subset) and 50 214 light images in (d), (h) and (l) (complete).