  The COMPASS Collaboration at CERN has investigated the reaction $\pi^- \gamma
\rightarrow \pi^-\pi^-\pi^+$ embedded in the Primakoff reaction of
$190~\textrm{GeV}$ pions scattering in the Coulomb field of a lead target,
$\pi^- \text{Pb} \rightarrow \pi^-\pi^-\pi^+ \text{Pb}$. Exchange of quasi-real
photons is selected by isolating the sharp Coulomb peak observed at momentum
transfer below $0.001~(\text{GeV}/c)^2$. Using a partial-wave analysis the
amplitudes and relative phases of the $a_2(1320)$ and $\pi_2(1670)$ mesons have
been extracted, and the Coulomb and the diffractive contributions have been
disentangled. Measuring absolute production cross sections we have determined
the radiative width of the $a_2(1320)$ to be $\Gamma_0(a_2(1320) \rightarrow
\pi\gamma) = (358 \pm 6_{\textrm{stat}} \pm 42_{\textrm{syst}})~\textrm{keV}$.
As the first measurement, $\Gamma_0(\pi_2(1670) \rightarrow \pi\gamma) = (181
\pm 11_{\textrm{stat}} \pm 27_{\textrm{syst}})~\textrm{keV} \cdot
(\textrm{BR}^{\textrm{PDG}}_{f_2 \pi}/\textrm{BR}_{f_2 \pi})$ is obtained for
the radiative width of the $\pi_2(1670)$, where in this analysis the branching
ratio $\textrm{BR}^{\textrm{PDG}}_{f_2 \pi}=0.56$ has been used. We compare
these values to previous measurements and theoretical predictions.
