As usual I’ll have a look at the technical data of the Sigma first. I’ve rated the features with a [+] (or [++]), when it’s better than average or even state of the art, a [0] if it’s standard or just average, and [-] if there’s a disadvantage. For comparison I use the Nikon 80-400mm f4.5-5.6G VR (“Nikon” for short) and the Canon EF 100-400mm f4.5-5.6 L IS II (“Canon”). Keep in mind that both the Canon and Nikon lenses are a third of a stop faster than the new Sigma. That may not seem much in light gathering power but it certainly is one of the major reasons for differences in price and weight. You can try to manually correct this inadequate vignetting profile using Lightroom’s additional adjustment sliders, but unfortunately, another problem pops up, one that is again becoming all too common on mirrorless lenses and cameras: the actual color of the corrected areas may look colder than the un-corrected center of the image, so you’ll wind up with faintly cool/blue looking image corners, or a faintly warmer central circle in the image. I use all of the focal lengths in this lens for landscape photography and usually carry a lens covering the 100-400mm range for such use. You could try mounting your camera on a tripod using a forward-aiming tripod plate that tries to balance out the setup a little bit, but based on my observations of the flex stress this puts on the bottom of the camera body itself, I DO NOT ADVISE THIS, unless you use one of those special long-lens support plates that actually reaches up to touch and support the lens. Reversed Zoom & Focus Ring Position

Regarding specs and measurements, the Sigma 100-400mm f/5-6.3 DG DN OS Contemporary Lens vs. Sony FE 100-400mm f/4.5-5.6 GM OSS Lens comparisonThe images were processed in Capture One using the Natural Clarity method with the sharpening amount set to only "30" on a 0-1000 scale. Above: This is an impressive result for the lens, but even more so when compared side-by-side to the Sony FE 100-400mm. Here’s the Sigma on the left at 100mm f5 and the Sony on the right at 100mm f4.5 and to me they’re delivering essentially the same detail in the middle, and in the corners too. If I am not using it as my primary lens, a lens covering the 100-400mm range is usually handling much of the balance of my needs, such as complementing a 600mm lens when photographing wildlife or a 24-70mm lens when photographing landscapes. AF accuracy is essential for realizing the ultimate image quality a lens is capable of, and this lens has delivered only accurately-focused images.

The handling of the Sigma 100-400mm f/5-6.3 DG OS HSM | C is excellent, as we said in our full review. The zoom and focus rings are smooth, and being able to twist the focus ring to override autofocus is a really useful feature for those times you need to be ultra-precise. The interior of the lens is ribbed to avoid light reflecting into the lens, and the front of the exterior is ribbed in the other direction to aid in grip during installation and removal. Corner sharpness does not always matter, but it does matter for many disciplines, including landscape photography. Allowing more light to reach the sensor permits freezing action and handholding the camera in lower light levels and can also permit use of a lower (less noisy) ISO setting. The substantially-sized, crisply-ribbed rubber zoom ring is very smooth with an ideal rotational resistance.

Sigma 100-400mm DN Autofocus Performance

At 150mm focal length the Nikon has a slight advantage in the APS-C/DX image-circle and the FF/FX-corner. A relatively common lens aberration is axial (longitudinal, bokeh) CA, which causes non-coinciding focal planes of the various wavelengths of light. At the top of this comparison priority list is the Sony equivalent model, the FE 100-400mm f/4.5-5.6 GM OSS Lens.

As a "DG" lens, it is compatible with all Sony E-mount mirrorless ("DN") cameras, including both full-frame ("DG") and APS-C sensor format models, Leica L-mount, and Fujifilm X mount. Well, this Mark II version is extensively redesigned from its predecessor, ditching the questionable trombone-style push-pull zoom mechanism in favour of a more conventional twist ring. More importantly though, the optical design has been updated for greater sharpness, which is impressive throughout the zoom range. In our lab tests we found a little drop-off towards the outer end of the zoom, but it was still very impressive. As I said in the beginning of this review, most photographers highly value a telephoto zoom lens with long focal lengths, a significant percentage of these photographers are looking for a lightweight, low cost option, and no one wants to give up great image quality or deal with a lens that does not perform well. Normal is for the scene to change size in the frame (sometimes significantly) as the focus is pulled from one extent to the other, referred to as focus breathing, a change in focal length resulting from a change in focus distance. The long end, typically more-easily used outdoors, will provide a more-compressed appearance (due to the longer subject distance).

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Above: It’s possible to achieve very shallow depth of field effects with telephoto lenses, especially if you’re close to the main subject. Here’s that decoration again from about 1.2m where, at 100mm f5, the fairy lights are rendered into attractive, soft-edged blobs. As you close the aperture down, the nine-blade system keeps the bokeh blobs fairy circular and there’s little to no onion-ringing. For comparison, here’s the Sigma next to the Sony, both at 100mm and their maximum apertures: f5 for the Sigma on the left and f4.5 for the Sony on the right. Despite the slightly larger aperture, the blobs on the Sony are roughly similar in size here, although they have slightly sharper edges. There’s no right or wrong here, only personal preference, although as you already know, the Sony can maintain its close focusing distance throughout the focal range, allowing much greater macro magnification than the Sigma. While you'll love those focal length ranges, the teleconverters have a negative impact on image quality — especially the 2x model. A downside to the variable max aperture is that the widest available f/4.5 max aperture cannot be used over the entire focal length range. Despite producing the relatively small image circle used by APS-C format cameras, the lens is about the same weight as competing Canon and Nikon full-frame compatible lenses. Thanks to the APS-C crop factor, the effective zoom range is boosted to 150-600mm and you can bump it up even more with one of Fujifilm’s 1.4x or 2x tele-converters, albeit with a loss of one or two f/stops in aperture width. As mentioned, those using an ASP-C/1.5x FOVCF sensor format DSLR will see an angle of view similar to a full-frame-mounted 150-600mm lens.

From the charts, overall contrast (red lines) from the new Sigma should be very high, even a bit better than from the Nikon. The green 30 lp/mm line(s) also indicates a very good resolution of fine details from the new Sigma at the long end with only some astigmatism in the last millimeters of the FF-corner. At the short end the new Sigma and the Nikon look pretty similar with the Sigma again producing a bit more astigmatism especially around the APS-C/DX corner. Let’s see how this theoretical performance translates into real life results in the sharpness test based on Siemens-stars.Above: The Sigma 100-400 DG DN employs 22 elements in 16 groups, just one more element than the DSLR version. The closest focusing distance is 1.12m at 100mm increasing to 1.6m at 400mm, compared to 0.98m for the Sony throughout its focal range; this allows the Sony to deliver much greater magnification on close-ups. The size of the ring is adequate, but this mold-indented ribbed plastic ring is flush with the lens barrel, making it somewhat difficult to find tactilely, especially with gloves on. At 400mm, most 1/40 second images were sharp, the keeper rate at 1/30 was reasonable, and some sharp images were made at 1/15 second.