Sigma APO 50-500mm f/4.5-6.3 DG OS HSM Nikon mount lens review: solid performance, accessible price

Introduction With more choice than either Canon or Nikon can currently offer, Sigma has an enviable range of telephoto zooms. Given the wider zoom range and a $1,659 price tag that comfortably undercuts the Nikon and Canon 80/100-400mm f/4.5-5.6 equivalents, this one sounds particularly tempting. Not only does this full frame lens boast an ultrasonic type (HSM) AF motor but it also has optical image stabilization, which Sigma claims allows shutter speeds of up to 4 stops slower than a non-stabilized model and a useful close focus capability of 1:3.1 set at 200mm. While the large