The sigma 17 50mm f28 ex dc os hsm lens with canon fit is an image stabilised standard zoom for digital slr cameras with an aps c sized sensor the lens covers a focal length from 17mm wide angle and offers a large aperture of f28 throughout the entire zoom range making it ideal for many types of photography including portraiture and landscapes alongside sigmas optical stabiliser the lens also includes a hypersonic af motor for quicker quieter focusing