Isolated-photon cross section ratio of pp collisions at $\sqrt{s}=$ 7 TeV from [49] (left) and $\sqrt{s}=$ 13 TeV from [67] (right) over $\sqrt{s}=$ 5.02 TeV in data and NLO calculation from JETPHOX for $R=$ 0.4. Error bars and empty boxes are the data statistical and systematic uncertainties, respectively. Filled boxes represent the theory scale (orange) and PDF (pink) uncertainties.