Nuclear photoreactions at intermediate energies

We review the interaction of real photons with nuclei up to the GeV region. The common microscopic description of exchange effects below threshold and of the corresponding real photoproduction above, is emphasized. The theoretical problems connected with π photoproduction in the Δ region and vector meson photoproduction are spelled out and solved. The gross features of the reaction mechanism are shown to explain both the low energy region, the bulk properties around the Δ(1241) resonance, as well as the appearance of shadowing only above the ϱ threshold.