Left: Isolated-photon differential cross section measured in \pp and \PbPb collisions at \snnfive for five \PbPb centrality classes for $R=0.2$. Error bars and boxes are the statistical and systematic uncertainties, respectively. The bands correspond to NLO pQCD calculations with JETPHOX, for \PbPb collisions calculated for the 0--100\% centrality class and scaled by \Ncoll. Right: Ratio of data over JETPHOX NLO pQCD calculations. The bands centred at unity correspond to the JETPHOX pQCD calculations, their width represents the scale (blue) uncertainty and PDF (orange) uncertainty. The normalisation uncertainties are not included in the left panel but they are shown in the right panel as a grey box on the left of each of the frames around unity.