Justement, il semblerait que si, notamment dans le cas d'un sujet en éloignement ou rapprochement rapide (cf test sur the digital picture):
Sigma 120-300mm f/2.8 EX DG HSM Lens Review

Je cites:
Unfortunately, the Sigma 120-300mm f/2.8 EX DG HSM Lens has a significant shortcoming that affects action sports photography - Autofocus can't keep up with action rapidly moving toward or away from the camera. People running to be more specific. I missed a significant number of shots when tracking action in AI Servo mode (on a Canon 1-Series body) - all focused behind the direction of the action

il semblerait quele nouveau modèle OS soit bien meilleur à ce niveau