We present a study of the decays B + → ρ + γ , B 0 → ρ 0 γ , and B 0 → ω γ . The analysis is based on data containing 347 × 10 6 B ¯¯¯ B events recorded with the BABAR detector at the PEP-II asymmetric B factory. We measure the branching fractions B ( B + → ρ + γ ) = ( 1.10 + 0.37 − 0.33 ± 0.09 ) × 10 − 6 and B ( B 0 → ρ 0 γ ) = ( 0.79 + 0.22 − 0.20 ± 0.06 ) × 10 − 6 , and set a 90% C.L. upper limit B ( B 0 → ω γ ) < 0.78 × 10 − 6 . We also measure the isospin-averaged branching fraction B ( B → ( ρ / ω ) γ ) = ( 1.25 + 0.25 − 0.24 ± 0.09 ) × 10 − 6 , from which we determine | V td / V ts | = 0.200 + 0.021 − 0.020 ± 0.015 , where the first uncertainty is experimental and the second is theoretical.