  We present a pion photoproduction model on the free nucleon based on an
Effective Lagrangian Approach (ELA) which includes the nucleon resonances
($\Delta(1232)$, N(1440), N(1520), N(1535), $\Delta (1620)$, N(1650), and
$\Delta (1700)$), in addition to Born and vector meson exchange terms. The
model incorporates a new theoretical treatment of spin-3/2 resonances, first
introduced by Pascalutsa, avoiding pathologies present in previous models.
Other main features of the model are chiral symmetry, gauge invariance, and
crossing symmetry. We use the model combined with modern optimization
techniques to assess the parameters of the nucleon resonances on the basis of
world data on electromagnetic multipoles. We present results for
electromagnetic multipoles, differential cross sections, asymmetries, and total
cross sections for all one pion photoproduction processes on free nucleons. We
find overall agreement with data from threshold up to 1 GeV in laboratory
frame.
