We show that if E is an ample vector bundle of rank at least two with some curvature bound on O P(E * ) (1), then E * ⊗ det E is Kobayashi positive. The proof relies on comparing the curvature of (det E * ) k and S k E for large k and using duality of convex Finsler metrics. Following the same thread of thought, we show if E is ample with similar curvature bounds on O P(E * ) (1) and O P(E⊗det E * ) (1), then E is Kobayashi positive. With additional assumptions, we can furthermore show that E * ⊗ det E and E are Griffiths positive.