The?28-70mm f/2.8 DG DN Contemporary Lens?for E-Mount & L Mount from?Sigma?is a versatile wide-angle to portrait-length zoom characterized by its f/2.8 constant maximum aperture. The design suits working in available lighting conditions while affording increased control over depth of field. More lightweight and compact than similar 24-70mm lenses, it's optical design incorporates two FLD and two SLD low-dispersion elements plus three aspherical elements that reduce a variety of aberrations to achieve high sharpness