![]() However, the pincushion distortion at 35mm is not extreme – we measured less than -0.5%. Oddly, as focal length increases from 24-35mm, the average shows a very slight increase in overall barrel distortion, while the corners experience a noticeable increase in pincushion. At 24mm, the average distortion approaches 0%, yet we start to see a bit of pincushion distortion starting to appear in the corners. At 18mm, there is about 0.5% of barrel distortion in the corners while only 0.3% for the average across the frame. We see a bit of barrel distortion at focal lengths wider than 24mm, but less than we might normally expect from a zoom. Just like CA and vignetting, distortion is nicely controlled, although not eliminated altogether. When stopped down to ƒ/4 and beyond, vignetting at all focal lengths is barely noticeable. Vignetting decreases notably when you hit ƒ/2.8 with less than or equal to a fourth of a stop of light loss. At all focal lengths, there's about a half to just shy of two-thirds of a stop of light loss. While there is still some vignetting at apertures wider than ƒ/4, it's not extreme and the amount of vignetting is consistent across all focal lengths. We also see well-controlled vignetting with the Sigma 18-35mm lens. a 300th), but as you zoom to the longer focal lengths, the difference between the corners and average shrinks appreciably. At 18mm, the corners show two times more CA compared to the average across the frame(about one 600th of a percent of the frame height vs. As expected, we saw more CA at the wide-angle focal lengths, but it drops significantly in both the corners and across the frame as you zoom to 35mm. The Sigma does quite well in controlling chromatic aberration. Overall, sharpness results for this lens are nothing short of stunning. Even at 35mm at ƒ/16, diffraction effects are not significant. As you can see in the Blur Index graph at right, variances in sharpness remain minimal at all apertures as you zoom out to 35mm. Even stopping all the way down to ƒ/16, diffraction limiting is really quite minimal. At ƒ/2.8, the overall frame appears extremely sharp. Stopping down at the wide end, between ƒ/2 and ƒ/2.8 appears to be the sweet spot, in terms of center sharpness. In this respect, it beats even many fast prime lenses in its focal length range. As we've seen time and again, very wide-aperture lenses (> ƒ/2.8) can often show significant corner softness when used at their widest apertures, but the Sigma 18-35 not one of them. At 18mm and ƒ/1.8, the Sigma shows very little corner softness and a good portion of the center and middle of the frame are very sharp indeed. This is an amazingly sharp lens, even wide open at ƒ/1.8, which is typically not the case with very wide-aperture lenses. ![]() New: Check out some real-world sample photos taken by our lens specialist Rob over our Flickr page! *Note that this lens review is based on a pre-production model. (And there really is no competition, when it comes to the ƒ/1.8 maximum aperture.) As you'll see below, this is an incredibly aggressive price when compared with competing models from the camera makers. Sigma is pricing this lens very competitively at a street price of just $799 for Canon, Nikon and Sigma mounts, with Sony and Pentax models coming soon. The Sigma 18-35mm ƒ/1.8 DC HSM "A" lens ships with lens hood, front and rear caps and a soft case. The Sigma 18-35 has separate zoom and focusing rings, as well as marked focal lengths (18, 20, 24, 28, 35mm) and a focusing scale. Canon 17-55 ƒ/2.8 IS USM), but the wide ƒ/1.8 aperture helps compensate for that allowing shutter speeds more than twice as fast in low light. The lens does not feature image stabilization like some of its rivals (e.g. As mentioned, unlike a lot of zoom lenses for APS-C cameras, the aperture of the Sigma 18-35 stays constant throughout the zoom range with maximum and minimum apertures being ƒ/1.8 to ƒ/16, respectively. On a camera with a 1.5x crop factor, the Sigma 18-35mm ƒ/1.8 features an approximate field of view range equivalent to a 27mm-52.5mm on a 35mm camera, making it a versatile all-around lens that encompasses a useful range of wide-angle to normal focal lengths. This makes it especially noteworthy among its competitors. ![]() This gives shooters the ability to not only photograph in much darker conditions but also produce a much shallower depth of field, compared to all other zoom lenses that only open up to ƒ/2.8 or smaller. Part of Sigma's new "Art" series, it is the first zoom lens anywhere to feature a constant ƒ/1.8 aperture. The Sigma 18-35mm ƒ/1.8 DC HSM "A" lens is a wide-angle to standard zoom lens designed for APS-C "crop"-sensor cameras.
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