In terms of specifications, finish, image quality and price we’re dealing with a “game changer”; that’s what we wrote in our review of the Sigma 18-35 mm 1.8 Art with a Canon 650D. Would this lens would be able to perform even better if you used it in conjunction with the 24 megapixel sensor sans moiré filter Nikon D7100?
And it does. Only the zoom range of the Sigma 18-35 mm Art is in terms of view angle slightly less than a 24-70 mm zoom lens on a camera with a full frame sensor. In addition, with the Sigma 18-35 mm f/1.8 Art and the Nikon D7100 (with APS-C sensor), you’ll get pictures with image quality and bokeh that rival those of more expensive, heavier and larger lenses on a camera with a full-frame sensor. That will save you a lot of money, because full-frame cameras and good, full-frame lenses aren’t cheap.

Sigma 18-35mm f/1.8 DC HSM A @ Nikon D7100

The angle of view (equivalent to a 29-53 mm zoom lens on a full frame camera) and the high, constant f/1.8 brightness make the Sigma 18-35 mm Art an ideal lens for many applications such as concert-, holiday-, street-, wedding- or journalism-photography.

Construction

A bright lens manufactured to professional standards, in terms of size and weight, cannot be compared with a standard kit lens. With a length of 12 inches, a filter size of 72 mm and a weight of 810 grams, the Sigma 18-35 mm Art makes a combination with an APS-C body that for an amateur photographer will take some getting to get used to.
For a professional photographer who’s accustomed to a full-frame camera with a 24-70 mm zoom lens, its length and weight just right.
The matte black appearance and high quality workmanship of the lens are the same as those of the Sigma Art 35 mm f/1.4 lens. The use of plastic, “Thermally Composite” (TSC), for the lens housing keeps the weight of the Sigma 18-35 mm Art somewhat limited.

Auto focus

The AF is of the USM-type, which not only results in fast and precise focusing, but it also offers the ability to manually override the AF at any time. The AF is accurate, silent and very fast. Probably partly due to the high brightness, the AF is also accurate in low light.
The Sigma 18-35 mm f/1.8 Art features internal focusing, meaning the length of the lens does not change and the filter mount does not rotate while focusing. Also with zooming in or out, the length of the lens remains unchanged. Especially when you close ups, where the front lens can get within 8 cm of the subject, this is quite nice.

Sharpness Sigma 18-35 mm f/1.8 DC HSM Art

When it comes to sharpness the Sigma 18-35 mm f/1.8 Art is among the very best in the category of lenses with a view angle of equivalent to a 28 mm, 35 mm or 50 mm lens on a camera with a full-frame sensor. The sharpness at maximum aperture is already very high. That’s remarkably good, because bright lenses at full aperture are usually somewhat fuzzier. After two stops stopping down, an even higher center sharpness is reached as well as the optimum sharpness at edges and in the corners. In terms of sharpness, with the Sigma 18-35 mm 1.8 Art you’re free to choose all the apertures between f/1.8 and f/11. That’s unique for a zoom lens.

Sigma USB dock

For 55 euros you can buy a USB dock with a Nikon mount for the Sigma 18-35 mm f1/8 Art, with which you can download firmware updates for this lens. You can also customize the combination of your camera with the Sigma 18-35 mm f/1.8 Art with four different distances. This option is particularly attractive for high resolution lenses with higher brightness than f/2.8, if you want to get the highest possible resolution. Our experience with the Sigma 18-35 mm Art can be found in the second part of our Sigma USB dock review.
Sigma 18-35 mm 1.8 Art @ 18 mm (HDR-images): When merging multiple shots into 1 HDR image, chromatic aberration is often more visible than in an ordinary picture. The Sigma Art lenses are attractive for HDR photographers, not only because of their insensitivity to flare, but also because of the low chromatic aberration.

Sigma 18-35 mm 1.8 Art @ 18 mm (HDR-image) When merging multiple images into one HDR image, chromatic aberration often becomes more visible than in a regular photo. The Sigma Art lenses are attractive for HDR photographers. Not only because of the insensitivity for flare, but also because of the low chromatic aberration.

SIGMA Mount Conversion Service

There’s is an interesting debate over whether the camera or the lens is the most important/most distinguishing instrument for a photographer. Sigma sees the choice of the lens as the center of the photography. If you ever want to switch to another camera brand, Sigma for the lenses from the Contemporary (C)-, Art (A)- or Sports (S)-lines have a unique feature. With the mount conversion service, your own lenses can be equipped with a lens mount from a different brand. The customization, which extends to exclusive features per camera brand, such as the OS function, are applied by Sigma in Aizu (Japan), so that the lens works optimally on the new body.
The mount conversion service is not guaranteed and is not cheap. The mount conversion service for the Sigma 18-35 mm Art costs € 200.00, including sales tax. This allows you to keep the lenses with which you are already familiar, because buying a new lens is substantially more expensive.

Vignetting

Given the high brightness of the Sigma 18-35 mm Art, it’s no surprise that there is any visible vignetting at maximum aperture. After two stops stopping down, only at f/4 then, the vignetting completely disappears. Both manually and using lens correction profiles, vignetting is simple and efficient to correct in Lightroom.

Vignetting carries very little weight in the final tally of our reviews. We try to correct the scores with: “What you see is what you get”. And many photographers aren’t bothered by vignetting, or even find it beautiful.

Distortion

The distortion of the Sigma 18-35 mm Art ranges from light barrel-shaped at a focal length of 18 mm to light pincushion-shaped at a focal length of 35 mm. This behavior is characteristic for a zoom lens with this focal length range.

To correct distortion in RAW files is easy using lens correction profiles in Photoshop or Lightroom. The scores for distortion for the Sigma 18-35 mm 1.8 Art at all focal lengths are higher than 9. The final score after correction for distortion would be 0.6 higher than at present.

Lens correction profiles in Lightroom: Usually, Lightroom automatically recognizes a lens. Click on “Enable Profile Corrections”, then the brand, model and the available lens correction profile automatically appear. With the Sigma 18-35 mm 1.8 Art this information does not appear (in Lightroom version 5.2). Fortunately, the lens correction profile is available. All you have to do is to select Sigma as the brand. The remaining information will appear and both the distortion and the vignetting in RAW files can be corrected with a single click.

Bokeh

Both background blur-blur and foreground blur in terms of character are strongly reminiscent of the OOF (“Out of focus”) of a lens on a camera with a full-frame sensor. Above you can see a partial enlargement of a picture made at a 24 mm focal length and f/1.8. At this focal length, you don’t get such a butter-soft bokeh like with a telephoto lens, but the combination of sharpness of the subject and the background blur are sensationally good. The Sigma 18-35 mm Art provides a very nice round bokeh of a bright light source in the background, as you can see in the image below.
Bright lenses almost all suffer from longitudinal chromatic aberration, which is also called color bokeh. You’ll get purple fringing behind the focus point and green edges in front of the focus point. Color bokeh only occurs with very bright lenses, and it disappears by stopping down. At f/2.8 or smaller you don’t see it. On the right, you can see a test shot made at f/1.8 for the detection of color bokeh. Class.

Flare

With the Sigma 18-35 mm f/1.8 Sigma’s Art, the designers surpassed themselves in terms of flaring. If there is a bright light source just outside image field, you will have no problems with flare, never mind whether you used the included lens hood. If you are shooting straight into the sun, so with the sun in full frame, then there is a small zone around the sun where flare can be seen. With effort, we were able to find in our test shots a rainbow-like ghost, which we circled in red in the image cutout on the right. Where flare’s concerned, we currently don’t know about any better zoom lenses. There are a ton of lenses with a fixed focal length that are more bothered by flare and ghosts. That seems to me an important consideration if you like HDR, night photography or concert photography.

Chromatic aberration Sigma 18-35mm f/1.8 DC HSM Art

Lateral chromatic aberration, magenta and blue-green edges at strong contrast transitions in the corners of the image, you will almost not find with this lens. We have the worst case that we found in our practice shots, shown here.

Conclusion Sigma 18-35mm f/1.8 DC HSM Art review

Pros

• Zoom lens with unparalleled high brightness
• Very high image quality
• Qualitatively equivalent to, or better than, lenses with a fixed focal lengths
• Nice bokeh/background blur: equivalent to full frame

  Cons

• Somewhat limited zoom range
• Visible distortion at the extremities of the zoom range

Because we had previously reviewed the Sigma 18-35 mm 1.8 Art on a Canon 650D, our expectations were high. Our test results for the Sigma 18-35 mm Art with a Nikon D7100 are in line with our earlier test for most image quality properties. The resolution is, thanks to the Nikon D7100, even higher than in our previous test of the Sigma 18-35 mm 1.8 Art on a Canon 650D. If you correct distortion of the Sigma 18-35 mm 1.8 Art in RAW files using the lens correction profiles for RAW files in Lightroom, then the scores for distortion at all focal lengths become a 9 or higher, and the final score falls 0.6 higher than the current final scores. With that, the combination of a Nikon D7100 with the Sigma 18-35 mm 1.8 Art in terms of picture quality beats almost all-DX, FX and both zoom and fixed focus lenses with a view angle equivalent to a 28 mm, 35 mm or 50 mm focal length on a camera with a full frame sensor. Wow.