18-250MM

The 18-250mm f/3.5-6.3 DC Macro OS HSM is the latest in a long line of all-in-one ‘superzoom’ lenses from Sigma, having been announced in June 2012. It offers two main developments over its predecessor, the confusingly similarly-named 18-250mm f/3.5-6.3 DC OS HSM – namely improved close-up capability (hence the ‘Macro’ moniker), and a significant reduction in size and weight. Sigma says the latter is due to the use of a ‘Thermally Stable Composite’ (TSC) material in the construction of the lens barrel. Sigma has included optical image stabilization in the lens design, promising the ability to hand-hold the lens at shutter speeds four stops slower than usual before camera shake becomes a problem. The lens features an ultrasonic-type ‘Hypersonic Motor’ for quiet focusing, which means it will autofocus on entry-level Nikon SLR bodies. Despite its improved close-focusing abilities, the optical formula is actually a bit simpler than its predecessors, and uses only a single Super-Low Dispersion glass element rather than four. Three aspheric elements are also used in the 16 element, 13 group design.