  This is the first of two papers in which we study real and virtual
photon-proton scattering in a nonperturbative framework. We classify different
contributions to this process and identify the leading contributions at high
energies. We then study the renormalisation of the photon-quark-antiquark
vertex that occurs in the leading contributions. We find something like the
dipole picture in one of these contributions but also find two correction terms
which can potentially become large at small photon virtualities. In the second
paper we will discuss the additional approximations and assumptions that are
necessary to obtain the dipole model of high energy scattering from the results
found here.
