  The multipole content of pion photoproduction at the $\Delta^+ (1232)$
resonance has been extracted from a data set dominated by recent Mainz
Microtron (MAMI) precision measurements. The analysis has been carried out in
the Athens Model Independent Analysis Scheme (AMIAS), thus eliminating any
model bias. The benchmark quantity for nucleon deformation, $EMR = E2/M1 =
E_{1+}^{3/2}/M_{1+}^{3/2}$, was determined to be $-2.5 \pm 0.4_{stat+syst}$,
thus reconfirming in a model independent way that the conjecture of baryon
deformation is valid. The derived multipole amplitudes provide stringent
constraints on QCD simulations and QCD inspired models striving to describe
hadronic structure. They are in good agreement with phenomenological models
which explicitly incorporate pionic degrees of freedom and with lattice QCD
calculations.
