[en] The scale dependence of the evolution of photoproduction cross sections with the photon-proton centre of mass energy W is studied using low Q² < 0.01 GeV² e⁺p interactions collected by the H1 experiment at HERA. The value of the largest transverse momentum of a charged particle in the photon fragmentation region is used to define the hard scale. The slope of the W dependence of the cross section is observed to increase steeply with increasing transverse momentum. The result is compared to measurements of the Q² evolution of the W dependence of the virtual photon-proton cross section. Interpretations in terms of QCD and in terms of Regge phenomenology are discussed. (orig.)