Left panel: the BPT [Nii] λ6584/Hα vs. [Oiii] λ5007/Hβ diagram. The location of SDSS galaxies is shown by the grey contours with the outermost contour encolosing 99% of the galaxies. The MUSE UDF sources are plotted in top with colour encoding the discrepancy between BPZ photometric and spectroscopic redshift as given by the colour key on top. Right panel: [Oiii] λ5007/[Oii] λ3727 vs. [Oiii] λ5007/Hβ diagram (see also Paalvast et al., in prep.) showing the same. The purple line and square shows the line ratios proposed for photo-z work by Ilbert et al. (2009).