Magnitude of the Gamma-Ray Burst GRB 050904 as observed with FORS2 and ISAAC in the various filters. The bandpasses of the ESO filters are overplotted as well as the best-fitting template which allowed the astronomers to measure the photometric redshift. The clear drop of the flux of the object in the I-band compared to the others is the telltale signature of a high-redshift object.