Sigma has recently announced their new lens for Pentax mount DSLR Camera. The new 28-300mm F3.5-6.3 DG MACRO is digitally optimized lens covers all the focal lengths from 28mm wide angle to 300mm telephoto with 10.7:1 high zoom ratio as well as macro capability.
The new multi layer lens coating and lens design reduce flare and ghost, which is a common problem with digital cameras and also creates an optimum color balance through the entire zoom range. This lens features two Special Low Dispersion (SLD) glass elements and four aspherical lenses for excellent correction of all types of aberration and displays a high level of optical ability. The use of aspherical lenses in the construction of this lens not only corrects aberrations but also produces a very compact and lightweight lens design.
The lens has a minimum focusing distance of 50cm at all focal lengths and is equipped with a macro mechanism for close-up photography at 300mm telephoto, allowing a reproduction ratio of 1:3. Moreover, the lens has internal focussing means that it has the advantage of a non-rotating front lens assembly, which is of great benefit when using polarizing filter and Petal-type hood.