![]() ![]() Shading or "vignetting" never gets real bad at the 10mm end, but then decreases relatively slowly as you stop down or zoom towards 20mm. (And even in the extreme corners, the coloration from the CA isn't as strong as we've seen with some lenses.) Average CA stays quite low as you zoom from 10 to 20mm, while the maximum value decreases quite rapidly, dropping to a very low level by 14mm. This is because the most severe CA occurs only at the extreme corners and edges of the frame, while most of the image area is quite clean. Actually, the maximum CA is high, while the average level is quite low. Where this lens does suffer somewhat at maximum wide angle is in the areas of chromatic aberration and light falloff ("vignetting") which were both on the high side. But they're not far off, to the point that it'll probably take a bit of pixel-peeping to see the softness anywhere at f/8. At 10-12mm, the corners don't really flatten out until you get to f/8, and even there, they're not quite crisp. At the 10mm end, the center is very sharp, but the corners get a little soft, but the corner softness decreases substantially as you move toward the "tele" end of its range, or as you stop down even a little from wide open. It wasn't perfect, and never got really *crisp*, but on the whole did quite a bit better than we had been expecting. In our testing, we were pleasantly surprised by how sharp this lens was wide open, across its focal length range. (Note that the image circle of this lens is most likely not large enough to adequately cover the sensor on a 1.3x camera.) ![]() I both cases, it covers a nice chunk of ultrawide territory. On 1.5x DSLRs like the Nikon and Sony/Minolta lines, it corresponds to a 15-30mm zoom, while on 1.6x cameras like the Canon Rebel and EOS 20/30D, it corresponds to a 16-32mm optic. As we've noted before, Sigma has really been leading the way with a large number of sub-frame optics, and one of their more notable achievements appears to be this 10-20mm superwide zoom. The major camera manufacturers and some of the third-party lens makers have begun to address this issue by making ultrawide-angle lenses with reduced image circles, specifically designed to work with sub-frame DSLRs. And that ultra wide-angle 17-35mm zoom turns into the equivalent of a 27 - 56mm. (Cameras adhering to the 4/3 standard have crop factors of 2.0, while some of Canon's pro DSLRs have a 1.3x crop factor.) What this means is that a lens that used to be a wide angle ends up being closer to a "normal" lens: For example, a 28mm lens on a 1.6x camera takes in about the same angle of view as a 45mm lens on a 35mm camera. This leads to what's commonly (but erroneously) referred to as a "focal length multiplier" or a "crop factor" that's typically in the range of 1.5 to 1.6x. This lens was another sweet little surprise from Sigma, delivering true ultrawide angle to cropped-sensor DSLRs, at a very attractive price, and frankly, with better optical quality than we expected for the price.Īs most are aware, one of the limitations of digital SLRs with sensors smaller than a 35mm film frame is that they capture a narrower viewing angle with any given lens than do their full-frame counterparts. A circular polarizing filter can also be used conveniently. The non-rotating lens barrel perfectly suits It has a minimum focusing distance of 24cm This lens is equipped with an inner focusing system, and the models which areĮquipped with HSM system provide quiet, high speed autofocus shooting and also One piece of glass mold and two hybrid aspherical lenses, offer excellent correction for distortion, as well as all types of aberration. ![]() Three SLD glass elements are employed for effective compensation of color aberration, which is a common problem with super-wide angle lenses. Wide angle of view (102.4 degrees at 10mm and 63.8 degrees at 20mm) offers the photographer greater freedom of expression. (From Sigma lens literature) Sigma 10-20mm f/4-5.6 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.
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