Typical of Sigma’s Contemporary line of lenses, the 100-400mm DG DN OS offers good performance in a compact and light package, at a competitive price. It comes up trumps for image quality, delivering excellent sharpness and contrast, while keeping fringing, distortions, ghosting and flare to a minimum. It’s pricier than the original DSLRmount DG OS HSM version of the lens, but the boost in image quality justifies the extra outlay.