Sigma’s exclusive OS system eliminates camera shake which is often a function of shooting at slower shutter speeds or with telephoto lenses. It reduces blur resulting from normal, minute shaking of a lens due to hand-held shooting. Sigma’s OS delivers a stabilized image where sharpness, at any given shutter speed, is increased dramatically. Sigma’s OS provides 4 stops slower with exposures 16 times longer. Sigma offers 8 lenses equipped with the OS system and does so in addition to delivering the highest quality lens at a most affordable price and available in all cameras mounts. Quality, selection and affordability; that is Sigma.