  Pion photoproduction is analyzed with the chiral Lagrangian. Partial-wave
amplitudes are obtained by an analytic extrapolation of subthreshold reaction
amplitudes computed in chiral perturbation theory, where the constraints set by
electromagnetic-gauge invariance, causality and unitarity are used to stabilize
the extrapolation. The experimental data set is reproduced up to energies
$\sqrt{s}\simeq 1300$ MeV in terms of the parameters relevant at order $Q^3$.
We present and discuss predictions for various spin observables.
