The tamron sp 17 50mm f28 xr di ii vc lens for cropped sensor digital cameras covers the very popular 17 50mm focal length range equivalent to 26 78mm in the full frame 35mm format making it extremely versatile its wide aperture provides practical advantages in low light shooting and image control giving you greater creative control the 17 50mm f28 xr di ii vc lens delivers impressive sharpness and contrast over its entire focal length and aperture range and at its maximum aperture of