Introduction

Sigma 10-20mm f/4-5.6 EX DC HSM is one of Sigma's professional grade ultra wide zoom lenses. The build quality of Sigma's EX marked lenses rivals that of Canon's L series lenses. This lens falls into this category - it looks and feels sturdy. Entire lens shell has rubberized finish that provides a good grip and superior look. Both zoom and focus rings are very smooth and the AF/MF switch is tight, ensuring that you won't switch it while hand-holding the lens. The lens bears DC designation, which indicates that it was specifically designed for APS-C type cameras and has a reduced imaging circle. The rear lens element of Sigma's DC lenses is not as protruding as Canon's EF-S lenses, meaning that the lens can be put on a full-frame camera and will not lock mirrors. In theory that is. Since the lens has a reduced imaging circle, it will produce heavy vignetting on a full-fram dSLR. Offering a field of view equivalent to 16-32mm on a full-frame camera, the lens is one of the widest zoom lenses for APS-C type cameras available on the market today.

Image

The lens construction consists of 14 elements in 10 groups, including three aspherical and three SLD (Special Low Dispersion) glass elements. Special coating has been applied to reduce flare and ghosting. Sigma 10-20mm f/4-5.6 EX DC HSM offers full-time manual and an HSM-type auto-focus, which is quite fast and relatively silent. The lens has a minimum focusing distance of 24cm (9.4") throughout entire zoom range, a maximum magnification of 1:6.7x at 20mm and weighs 465g (16.4oz). The lens is quite compact at 84x81mm (3.3x3.2in). Sigma advertises the lens as one with inner focus system - this is a bit misleading, since the lens actually extends slightly during zooming, but the front element of the lens does not rotate, allowing attaching a circular polarizer. The filter size is 77mm.

The factory box includes the Sigma 10-20mm f/4-5.6 EX DC HSM lens, front and rear caps, petal shaped lens hood, lens case, manual and warranty card. At about US$450 (as of February 2007) the lens is priced quite aggressively and undercuts its main competitor, Canon EF-S 10-22mm f/3.5-4.5 USM by a couple hundred bucks.

 

Summary
Lens Composition 14 elements in 10 groups
Angular Field 102-64 degrees
Minimum Focus 24cm/9.4in
Focusing Action AF/MF
f-stop Scale f/4-f/22, camera-controlled
Filter Size 77mm
Lens Hood Petal shaped (included)
Weight 465g/16.4lb
Dimensions 84x81mm/3.3x3.2"
Lens Case None

 

Field Tests

My first impression of the lens was that it was heavy - it is not a brick like one of the super telephoto lenses, but it was noticeably heavier then any other ultra wide zoom I tested to date. Not that it bothered me - on the contrary, weight added to the overall impression of sturdiness.

The lens produced noticeable distortion at 10mm, which again is expected from such a wide angle zoom lens. To a naked eye the distortion manifests itself as stretched objects in the corners of the image. Distortion actually exists throughout entire focal length but is significantly reduced at 20mm. Vignetting, which is quite common in ultra wide zoom lenses, is also present and is worst at 10mm. Stopping down to f/5.6 or f/8 helps reduce the problem.

Images taken with the lens are crisp in the center and somewhat softer at borders. And while overall border quality is worse then quality in the center, it remains consistent throughout focal range and does not fall completely apart as with some other lenses. Chromatic aberration was present across the focal range, but could be considered moderate for an ultra wide lens at 10mm and minimal at 20mm.

 

 

Lab Tests

Sigma 10-20mm f/4-5.6 EX DC HSM demonstrated outstanding results in the lab. Astonishingly, the lens especially excelled at 10mm! Sharp across various apertures, the lens would produce great 16in prints when stopped down to f/8. You would even get decent looking 19in prints assuming you stay with the same aperture, The lens got softer at the longer range, but even then, center remained as sharp as ever, with most of the softness showing at the borders. Conclusion? Very well balanced results, rivaling those of much more expensive lenses from other manufacturers (namely Canon). The lens truly deserves its European TIPA award as the best consumer lens in 2006.

 

MTF50 (Line Width / Inch on the Print) @ 10mm
MTF50 (Line Width / Inch on the Print) @ 10mm

 

MTF50 (Line Width / Inch on the Print) @ 17mm
MTF50 (Line Width / Inch on the Print) @ 17mm

 

MTF50 (Line Width / Inch on the Print) @ 20mm
MTF50 (Line Width / Inch on the Print) @ 20mm

Chromatic aberration was pretty minimal even wide open at 10mm - ~1pixel, and when stopped down practically non-existent. This was consistent throughout the supported zoom range, which can be considered an outstanding result for an ultra-wide zoom lens.

 

Image borders @ 10mm (100% crop): f/4 vs f/8
Image borders @ 10mm (100% crop): f/4 vs f/8

 

Alternatives

Matching this Sigma lens' bang for the buck is hard, but there are several alternatives on the market that you might want to consider. Firstly, as mentioned earlier, Canon EF-S 10-22mm f/3.5-4.5 USM (review) will be the primary competitor. Canon's lens is also designed for APS-C type cameras and performs quite well. It is however priced a few hundred dollars higher, so one must obviously ask whether it makes sense to shed that kind of money for some marginal improvement in image quality. Then there is Tokina AT-X 124 PRO DX AF 12-24mm f/4 (review), which is also priced at the same level as Sigma's lens and manages to stand its own ground in both build and image quality. Canon EF 17-40mm f/4L USM (review) comes to mind, but this lens is slightly more expensive and is not as wide as Sigma.

 

Recommendation

Sigma 10-20mm f/4-5.6 EX DC HSM is a great value for your money. The lens is one of the widest zoom lenses for APS-C dSLRs available on the market. Its build quality matches (and some might even claim exceeds) that of a Canon's L lens. Image quality rivals other ultra wide zooms on the market. Distortion that plagues the lens across entire focal length is something to be aware of, but considering that I have yet to see an ultra wide zoom that does not show any distortion, I would not stress too much about it. Given its aggressive price, Sigma 10-20mm f/4-5.6 EX DC HSM should remain at the top of your shopping list. Assuming you're OK investing in an APS-C type lens that is.