Description
The 10-20mm F4-5.6 EX DC HSM is Sigma’s offering in the APS-C ultrawide zoom sector, first announced in February 2005. It was introduced amongst a flurry of announcements as manufacturers raced to provide wideangle zooms for the burgeoning APS-C format DSLR market, with similar offerings also appearing in short measure from the likes of Tamron and Tokina (not to mention all of the major camera companies). It has since become a very popular lens, due in no small part to offering the joint-widest angle of view of all the APS-C ultra-wide zooms, while being available in mounts to fit all of the major DSLR systems. Equally it’s not hurt by having a very competitive price; it’s notably much cheaper than the camera manufacturers’ own offerings in this sector.
The optical formula features 14 elements in 10 groups, including three Super-low Dispersion glass elements for the minimization of chromatic aberrations, and three aspherical elements to reduce distortion and other aberrations. Users of Canon, Nikon, Sigma, and Four Thirds cameras benefit from an ultrasonic-type ‘HyperSonic Motor’ (HSM) for fast and silent autofocus, while the Pentax and Sony mount versions use the ‘screw-drive’ coupling from the camera body. The ‘DC’ designation indicates that this lens is designed for DSLRs with APS-C or smaller sensors, and isn’t suitable for use on a full-frame body (the image circle isn’t large enough, and vignetting will occur).
