Study of $b \to d \gamma$ transitions with BaBar

Making use of a sum of exclusive final states with up to three charged pions and one neutral pion or eta, we have demonstrated that it is possible to measure the ratio of the inclusive rates $b \rightarrow d \gamma$ and $b \rightarrow s \gamma$. This provides a determination of $|V_{td}/V_{ts}|$ that is complementary to using the exclusive modes $B \rightarrow \rho \gamma$ and $B \rightarrow K^*\gamma$.