Super wide-angle zoom lens designed exclusively for digital SLR cameras.

This ultra-wide zoom lens has a wide angle of view from 102.4 – 63.8 degrees (when Sigma mount is used) and it is exclusive to digital SLR cameras. SLD glass elements effectively compensate color aberration. Aspherical lenses provide maximum correction for distortion and various aberrations; high image quality is displayed throughout the entire zoom range. The HSM equipped models makes fast AF speeds and quiet shooting a reality, and it is also capable of full-time manual focus. It has a minimum focusing distance of 9.4″ (24cm) at all focal lengths. It is also equipped with an integral Petal-type hood to block out extraneous light.

Ultra-wide zoom lens
10-20mm F4-5.6 EX DC HSM lens allows enjoyment of super wide-angle photography and it is a very powerful tool for indoor shooting and landscape photography with APS-C size image sensors of digital SLR cameras. Wide angle of view 102.4-63.8 degrees (for Sigma mount) offers the photographer greater freedom of expression.

Most Appropriate Coating for Digital SLR Cameras
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.

The best possible correction of aberrations
Three SLD (Special Low Dispersion) glass elements are employed for effective compensation of color aberration, which is a common problem with super-wide angle lenses. One piece of glass mold and two hybrid aspherical lenses, offer excellent correction for distortion, as well as all types of aberration.

Inner focus system
This lens incorporates an internal focusing system, which eliminates front lens rotation allowing the use of a Petal-type Hood and also minimize fluctuation of aberration caused by focusing system.

HSM (Hyper Sonic Motor)
The HSM equipped models ensure a silent, high-speed AF function as well as full-time manual focusing capability for Sigma, Canon, and Nikon-D mount lenses.

Minimum focusing distance of 9.4″ (24cm) at all focal lengths
This lens has a minimum focusing distance of 9.4″ (24cm) throughout the entire zoom range.

Read more at Sigma

Reviews

Sigma 10-20mm 1:4-5.6 EX DC HSM review by Andy Westlake, March 2009 (DPReview.com)

The Sigma 10-20mm F4-5.6 EX DC HSM is, on paper at least, a very attractive option for APS-C users looking for an ultra-wideangle zoom. The standout selling points are undoubtedly that 10mm wideangle view and the HSM focusing motor, which when coupled with Sigma’s traditionally keen pricing, makes for a compelling overall package. In the flesh that promise is to a great extent realized; optically the lens is a solid if not outstanding performer, build quality is up to Sigma’s usual standards, and the focusing is indeed fast, silent and accurate. So far, so good.

Delve a little deeper, though, and problems start to appear. Distortion at wideangle, with its hefty barrel effect localized towards the corners of the frame, can be highly detrimental for architectural shots, and to compound the issue it’s difficult to correct in software. But the bigger question mark hangs over the lens’s sharpness, and in particular its inconsistency through the zoom range and across the frame. It’s fine at 10mm and between 17 and 20mm, where stopped down to F8 or F11 results are firmly within the ‘green zone’ on our widget (corresponding to a critically sharp print of at least 12″ x 8″ / 30 x 20 cm). But in the intermediate range it’s simply soft across much of the frame, even at F11. This is compounded by curvature of field effects which can lead to some odd real-world results, as objects which would be expected to fall within the depth of field can sometimes be rendered unexpectedly soft. As a result, extra care in focusing is advisable, especially when shooting at relatively close distances – in such instances it’s best to use off-centre focus points (or even better, manual focus in live view) to make sure the subject is properly sharp.

Comparison to other wideangle zooms we’ve tested recently suggests the Sigma’s class-leading days may be numbered. On APS-C, it simply can’t match the biting central sharpness of the Tamron 10-24mm F3.5-4.5 Di-II in the 10-18mm range (for which, we suspect, users will mainly be buying this type of lens), and has more problematic distortion characteristics. However in a typical case of swings and roundabouts, the Sigma shows superior sharpness when shot wide open, and is better in the corners of the frame at all settings; it also has lower chromatic aberration, is better built and uses a superior focusing system. On Four Thirds, the new Olympus Zuiko Digital ED 9-18mm F4-5.6 offers a wider angle of view and markedly superior optics in a lighter and more compact package; so while it’s more highly priced, on balance it’s a better buy for most users.

So overall the Sigma 10-20mm F4-5.6 EX DC HSM is a solid, well-built lens with good operational characteristics, which justifies its popularity with generally decent imaging results. While its long-running unique selling point of being the only third-party 10mm zoom has now disappeared, and it faces strong competition from Tamron’s 10-24mm, the different characteristics of the two lenses means it’s still a good option for APS-C users looking for the widest of ultra-wideangle zooms. It may no longer necessarily be the leader of the pack, but it’s still well worth considering.

Conclusion – Pros

• Equal widest angle in its class.
• Very low chromatic aberration.
• Fast and silent HSM autofocus.
• Good build quality.

Conclusion – Cons

• Rather inconsistent sharpness (partially due to curvature of field).
• Pronounced, complex distortion at 10mm.

Sigma 10-20mm f/4-5.6 EX DC Interchangeable Lens Review by ephotozone.com

With the wide field of view that this lens gives the digital SLR owners that require panoramic style angles, this lens is an answer to their prayers. The performance is excellent and the size and weight is little more than a standard zoom. Aimed at an area where there are no contenders stepping down from the 35mm arena and fulfilling a definite need, Sigma should be onto a winner here.

In summary the main positive points of the Sigma 10-20mm f/4-5.6 EX DC are:
Good performance, nudging excellent at the wide end.

• Ability to use standard filters
• Weight, size and handling
• Price

Negative points are:

• Softish edges in middle of range.
• Slight pincushion at 20mm end.