  Tagged linearly polarized photons have been used at the Mainz Microtron MAMI
for simultaneous measurements of the p(\vec{\gamma},p)\pi^0 and
p(\vec{\gamma},\pi^+)n reaction channels to study the \gamma N \to \Delta(1232)
transition. The energy dependence of the magnetic dipole M_{1+}^{3/2} and
electric quadrupole E_{1+}^{3/2} amplitudes have been extracted from these data
in the photon energy range from 270 to 420 MeV. The E2/M1 ratio for the \gamma
N \to \Delta(1232) transition has been determined to be -
(2.5+-0.1_{stat}+-0.2_{sys}) % at the resonance position delta_{33}=90^0.
