The Sigma 18-50mm f/2.8 EX DC HSM Macro Lens now incorporates the HSM feature, which gives this lens the capability to auto focus with all Nikon DSLR cameras (including the D40 and D40x). In addition, with the HSM (Hyper Sonic Motor) incorporated into this lens, focusing will be quieter and more responsive.
The 18-50mm f/2.8 EX DC HSM Macro Lens has a maximum magnification rating of 1:3, with a minimum focusing distance that is as close as 7.9" (20 cm), which makes it ideal for close-up photography. This lens is exclusively designed to suit the characteristics of digital SLR cameras. The characteristics of digital SLR cameras were taken into consideration when designing the lens power layout. The advanced lens design corrects various aberrations. This lens provides the utmost correction against lateral chromatic aberration which is a serious problem for digital SLR cameras.
This lens is also specially coated to get the best color balance with a digital camera, while also cutting down flare and ghost caused by reflections from the digital image sensor and lens. It has correction for vignetting and superior peripheral brightness is ensured. Ideal as a standard quality zoom lens with added macro capability, this lens provides an equivalent range of approx. 27-75mm when used with a Nikon digital SLR camera (*).
DC lenses are exclusively designed for digital SLR cameras. The image circle (rear of lens) is made to match the smaller dimensions used for the image sensor on digital cameras. As a result these lenses are also more compact and lightweight, and are better matched to digital SLR cameras.