  We study the effects of the $\Delta$(1232) resonance as an effective degree
of freedom for charged and neutral pion photo-production on nucleons. Different
observables have been calculated for these processes by using relativistic
chiral perturbation theory up to $\mathcal{O}(p^3)$ in the $ \delta$ counting,
thus, including pion loops. We compare our model with a large database
containing the available experimental data and constrain some unknown low
energy constants.
