For this test, we used the brand new Nikon D850 and we outfitted it with 24-70mm 2.8 lenses by Nikon, Sigma, and Tamron. In the past, third party lenses weren't even close in build quality or image quality when compared to a Nikon or Canon equivalent, but I'm happy to say that both Sigma and Tamron has really improved their lenses in the last few years while keeping their prices extremely competitive. We have come to expect Sigma Art lenses to by synonymous with great image and build quality at a competitive price.

Sigma 24-70mm F/2.8 DG OS HSM A for Nikon review - DXOMARK Sigma 24-70mm F/2.8 DG OS HSM A for Nikon review - DXOMARK

The zoom mechanism is damped well and is very smooth to operate, only tightening slightly at the telephoto end of the range. I had no issues with zoom creep during use either as the mechanism provides ample resistance to prevent the lens zooming under its own weight. The hood is strong molded plastic-constructed with only a slight amount of flex (which is good for absorbing impact). That aptly describes this lens with the wide end showing just a slight touch of mustache/wave distortion along with the normal central bulge of the barrel distortion.

The effect of different colors of the spectrum being magnified differently is referred to as lateral (or transverse) CA (Chromatic Aberration). But in other cases, I need several paragraphs to explain the complicated image quality a lens delivers. Stopping down to f/4 shows a very noticeable improvement and performance at f/5.6 is, again, quite good.

24-70mm F2.8 DG DN - SIGMA Corporation Support | 24-70mm F2.8 DG DN - SIGMA Corporation

The Canon's rear-positioned zoom ring is a much better design, but for sure you will like the Sigma's roughly-25%-lower price tag better. The Sigma 24-70mm f/2.8 DG OS HSM Art Lens features a dust/splash-proof construction including a rubber gasket seal at the lens mount. Though it feels like a solid chunk of lens in the hand, the 24-70mm Art lens is not that heavy and I didn't feel burdened even when carrying it on a nearly-4-mile hike in the national park. In recent years, that mutual exclusion has been disappearing and the combination option has been made available by a number of lens manufacturers.A requirement for a sharp image is that subject details do not cross over image sensor pixels during the exposure. The non-VR Nikon option is more-attractively priced than the VR counterpart, but it is still considerably more expensive than the Sigma. Coma becomes quite visible mid-frame and in the corners of images captured at wide apertures and significantly resolves when the lens is stopped down. The Nikon has less peripheral shading at the ends of the focal length range and the Sigma shows fewer flare effects at the wide end.