The tamron sp af17 50mm f28 xr di ii ld aspherical if is a lightweight compact fast standard zoom lens designed exclusively for digital slr cameras the focal length of this lens is equivalent to approx 26 78mm in 35mm format this lens offers an f28 maximum aperture throughout the entire zoom range to ensure stress free photographic shots at all focal lengths and distances additionally a broader photographic expression through the use of faster shutter speeds as a result of the max