  We study the N-Delta-gamma transition in the Dyson-Schwinger approach. The
nucleon and Delta baryons are treated as quark-diquark bound states, where the
ingredients of the electromagnetic transition current are computed
self-consistently from the underlying dynamics in QCD. Although our approach
does not include pion-cloud effects, we find that the electric and Coulomb
quadrupole form-factor ratios R_EM and R_SM show good agreement with
experimental data. This implies that the deformation from a spherical charge
distribution inside both baryons can be traced back to the appearance of p
waves in the nucleon and Delta bound-state amplitudes which are a consequence
of Poincare covariance. On the other hand, the dominant transition amplitude,
i.e. the magnetic dipole transition form factor, underestimates the data by
~25% in the static limit whereas agreement is achieved at larger momentum
transfer, which is consistent with missing pion-cloud contributions. We
furthermore find that the static properties of the form factors are not very
sensitive to a variation of the current-quark mass.
