The Sigma 10-20mm f/3.5 EX DC HSM Autofocus Zoom is a super-wide angle lens with a maximum aperture of f/3.5 throughout the entire zoom range, ensuring high image quality. The maximum aperture of f/3.5 allows enough light in to make it a great choice for indoor shooting as well as landscapes and creative portraiture.
With its wide angle view from 102.4 degrees, this lens can empower the photographer to produce creative images with exaggerated perspective. This lens has a Super Multi-Layer coating that coating reduces flare and ghosting. With a HSM (Hyper-Sonic Motor), the lens operates quietly and at high speed in both autofocus and full-time manual modes.
The lens design incorporates an inner focusing system which eliminates front lens rotation, making the lens particularly suitable for using the Petal-type hood, reducing extraneous light and reducing internal reflection.
Two ELD (Extraordinary Low Dispersion) glass elements and a SLD (Special Low Dispersion) glass element provide excellent correction of color aberration. Four aspherical lenses provide correction for distortion and allow compact and lightweight construction. This Sigma lens has a minimum focusing distance of 9.4 inches (24cm) throughout the entire zoom range and a maximum magnification ratio of 1:6.6.
The individual pieces of glass that form the overall optical construction. Most lenses have between four and eleven elements to bend the light rays to ensure a perfectly formed image appears on the light sensitive surface, such as a film or CCD. The elements are arranged in groups and may be seen in specification sheets as, for example, 6 elements in 4 groups. That configuration may have two single elements and the other four grouped in pairs.
A lens with a 1:1 magnification factor produces a projected image on the sensor which is the same as the subject. A 1:1 magnification factor is usually considered the minimum for a lens to be described as a “macro” lens. Specialist macro lenses are often 1:3 or even 1:10 magnification factors, meaning that 1mm across the subject becomes 3mm or 10mm when projected onto the sensor, thus 3 or 10 times magnification.