The Sigma 70-300mm f/4-5.6 DG OS is a lens marketed by the production company of the same name which is a popular choice among budget-conscious photographers who want a functional model with good performance. Some additional features typical of previous versions have been eliminated, however at the same time an optical stabilization system has been integrated capable of supporting shutter speeds up to four stops slower than normal. In this way it becomes possible to obtain much sharper and more precise images, eliminating much of the chromatic aberrations and distortions caused by exposure that does not conform to standards. This lens is characterized by being quite light and easy to handle, with a smooth zoom action, as well as being compatible with most full-frame digital reflex cameras. Its structure is mostly made of high quality plastic materials, so as to have a high level of resistance. Instead the lens mount is made of metal. A powder coat finish has been applied to the lens. The focusing is powered by a standard micromotor: it is a quieter solution when it comes to the manual system, while the automatic one is slightly noisier. Also remember that AF speed is slower in low light conditions. Another thing to consider is the fact that the front element rotates during autofocus and this can be problematic when using polarizers or graduated filters.