The Sigma 10-20mm f/3.5 EX DC HSM Autofocus Zoom is a super-wide angle lens with a relatively bright f/3.5 maximum aperture throughout its zoom range, helping to ensure high image quality. The lens gathers enough light to make it a great choice for indoor shooting as well as landscapes and creative portraiture. This version of the lens is exclusively made to fit the Pentax lens mount. It is not intended for use in "full frame" digital SLR cameras, or for any film-based cameras.
With a wide angle viewing range of 102.4-63.8°, this lens can empower a photographer to produce creative images with exaggerated perspective. Its Super Multi-Layer coating reduces flare and ghosting. The HSM autofocus motor provides quiet, high speed operation. You can also shoot with manual focus.
The 10-20 f/3.5 EX DC HSM incorporates an inner focusing system to eliminate front lens rotation, which enables the lens to use the included petal-type bayonet hood to eliminate extraneous light from striking the front of the optic. Two ELD (Extraordinary Low Dispersion) glass elements and a SLD (Special Low Dispersion) glass element provide excellent color fidelity, and 4 aspherical lens elements provide correction for common distortions.
This lens has a minimum focusing distance of 9.4" (24cm) throughout the entire zoom range, and a maximum magnification ratio of 1:6.6.