![]() Software can usually remove chromatic aberration when processing RAW files, but its effect on sharpness can be difficult to correct. But this is mostly present in the corners of the frame and will likely only be noticeable along high-contrast edges. Closing down the apertures increases sharpness to f/5.6-8, whereas after at f/11, all three begin to exhibit some diffraction and score below 70% acutance.Īll three models exhibit some lateral chromatic aberration - and it would be unusual if large-aperture zooms like this didn’t - but the Art series model not only has lower levels, it’s mostly restricted to the 24-28mm focal lengths.īoth the earlier model and the Nikkor have higher levels of aberration than the Art lens up to 50mm, and somewhat beyond for the Sigma’s predecessor. The acutance profile below shows the sharpness profile of the three lenses at their longest focal length and at f/2.8. Even so, while the Art series lens consistently beats both the earlier EX model and the pricier Nikkor lens, we noticed some astigmatism (where the horizontal and vertical acutance lines aren’t always close) at 24mm, and sharpness levels drop at 70mm. When looking more closely at the results, we can see that Sigma has gone to great lengths to achieve a more consistent level of sharpness, particularly wide-open at f/2.8. Still, we were expecting a greater increase in sharpness over the previous model. In case you’re wondering, the Sigma isn’t a match for the Canon, which retains its position as the gold standard for this category.) Sharpnessįrom our tests, it is clear Sigma prioritized sharpness across the frame (that is, the image field) at each focal length and aperture over outright sharpness, something that we’re seeing more frequently with modern designs. (In our our test of the Canon-mount version, you’ll get an idea of how the Sigma Art lens fares against the Tamron and Canon models. We tested all three lenses on the full-frame 36MP Nikon D810 to make the results directly comparable. ![]() In this section, we’re going to compare the Art series lens with the original Sigma 24-70mm IF EX DG HSM lens and the stabilized Nikon AF-S Nikkor 24-70mm f/2.8E ED VR. ![]() The two main third-party rivals from Tokina and Tamron share a similar overall level of optical quality, with the former boasting marginally higher sharpness levels when stopped down, and excellent transmission. Intriguingly, the latest Nikkor and its predecessor can’t quite match the performance of the third-party offerings, though they’re very close despite both having quite high levels of lateral chromatic aberration. The Sigma Art series 24-70mm f/2.8 lens’s overall score of 31 on the Nikon D810 puts it 5 points behind the maker’s 24-35mm f/2, which is a noticeable margin. Sigma is more active than anyone else in this space, with not only an Art series 24-70mm f/2.8, but also a faster and shorter-range 24-35mm f/2, so it’s interesting to compare the performance of these with others lenses sharing a Nikon mount, including the well-liked Nikon model and its equally-respected predecessor. Image quality compared to its competitors Like others in this group, there’s a noticeable drop in sharpness at 70mm. ![]() We achieved the best results at mid-range, at 35 and 50mm, but it is a good performer at the wider end as well, albeit with some astigmatism. Our results show that sharpness is slightly improved overall, especially when used wide-open at f/2.8 from corner to corner and at the mid- and longer focal lengths where large-aperture zooms tend to struggle (even high-grade models). ![]() With an overall score of 31 on a Nikon D810 body - one of the best performing cameras available (but now superseded by the D850), the Sigma 24-70mm f/2.8 DG OS HSM A improves upon the previous Sigma 24-70mm f/2.8 IF DG HSM model, which achieved a score of 25 on the same body. However, at 107.6 x 88 mm (4.2 x 3.49 in) and 1.02 kg (36 oz), it’s quite a bit bigger and heavier than the lens it replaces, which measures 95 x 89 mm (3.73 x 3.5 in) and weighs 0.79 kg (27.87 oz). Sigma is also keen to point out that it has adopted high-grade aspherical lens elements to reduce aberrations, while at the same time paying close attention to the shape of the bokeh. In addition, the large-diameter zoom features an image stabilizer unit. It has 19 elements arranged in 14 groups, with 3 low-dispersion elements to reduce chromatic aberration. Internally, Sigma says they’ve updated the optical construction to meet the demands of ultra-high-megapixel cameras. Sigma introduced the Art version of its 24-70mm f/2.8 lens in February 2017, bringing with it the familiar-looking exterior design with a mix of metal and “thermally stable composite” material, along with rubber sealing around the mount. ![]()
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