Review: SIGMA 24-35 mm F/2 | A by Banu Prakash.

DSC_5127.JPG Banu Prakash says “The first step in selecting a lens should be to insure that the focal length is optimal for the desired uses. The 24-35mm range covers the extreme upper end of what has long been considered “ultra-wide” (or 1mm over it depending on your definition) through simply-wide angles. While 24-35mm is a short range of focal lengths, those it has are very useful and very popular. The current lenses covering this focal length range, or a single focal length contained in that range, is huge.

Landscape photography is an especially great use for a 24mm lens. This focal length is quite wide and allows an entire scene to remain in focus, but 24mm is not so wide that it complicates landscape composition. A very high percentage of my landscape images have been captured at 16mm.
Architectural photography, large product photography, interior photography, birthday parties … are some uses for the entire focal length range.

Wedding and event photographers can often utilize these wide angles for capturing the overall scene, for environmental-type portraits and for even large-sized group portraits in tight spaces. At the 35mm end of the range, loosely framed individual portraits will have a nice perspective. Photojournalist’s needs are often similar to those of a wedding photographer and can also make use of this range.

Falling into the range of focal lengths I would want for fixed focal length general purpose use, the 35mm focal length is a great choice for capturing a natural perspective on a wide variety of subjects. It is wide enough to capture the big scene but not so wide that people and other subjects are readily distorted by the close perspective invited by ultra wide angles and not so wide that a nice background cannot be easily achieved.

When combined with a very wide aperture, this entire range is a good choice for night sky photography. The Milky Way stays relatively large in the frame at 24mm while star trails are only beginning to become challenging at 35mm.
While telephoto lenses are more frequently used for sports, a 24-35mm angle of view allows a very different perspective on these events. This focal length range can be used to capture the big picture of the venue, overhead shots of the athletes and their coaches being interviewed after the game and, when access and safety permit, full body environmental action sports photos showing lots of venue in the background.

Unmatched in a full frame compatible zoom DSLR lens is the wide f/2.0 max aperture. No other such zoom lets in more than 1/2 as much light. As a fixed max aperture lens, the f/2 aperture is available not only at the widest angle, but over the entire focal length range. Wide open exposure settings can remain unchanged during a full focal length extent adjustment.

Use the wide aperture to stop action in low light, to enable handholding in low light (though an image stabilized lens has the advantage with motionless subjects) and to create a strong background blur. Strong blur is a relative term as wide angle lenses are not nearly as good as telephotos at this task. The sign in the sample below is about 8′ (2.4m) away from the camera with the longest focal length (35mm) in use. At full resolution, the background blur is strong, but at reasonable web page resolution, the background subjects are easily discernable.

An extreme wide aperture is an incredibly useful feature, but … lenses often do not perform their optical best at their widest apertures and I was anxious to see what this lens delivered at f/2. Of primary concern for me is image “sharpness”, a term loosely used to describe resolution and contrast along with the effects (or lack of) caused by other aberrations.

At f/2, the Sigma 24-35mm f/2 DG HSM Art Lens delivers usably sharp images with sharpness decreasing slightly from 24 through 35mm. Usably sharp, but you might want to add more sharpness and contrast than normal to remove the slightly hazy appearance. The sharpness improvement seen at f/2.2 is very noticeable – noticeable enough that you may want to give up that 1/3 stop difference in aperture opening to gain the image quality benefit. At f/2.2, 35mm still trails in regards to sharpness over the entire focal length range. I would describe the center of the frame as very sharp at 24mm f/2.2 with the 35mm end reaching this level at f/2.8. Only a slight sharpness increase is seen in the center at narrower apertures.
With a wide angle, wide aperture lens, some vignetting can be expected when the lens is used at the widest aperture. In the case of this lens, the vignetting profile remains similar over the focal length range with about 2.5 stops showing in the full frame corners. Stopping down to f/2.8 drops the peripheral shading levels to about 1.4 stops and at f/4, an average of .7 stops remains (below visibility in many scenes). Stopping down further results in little change with about .5 or .6 stops remaining at f/16.
At wide apertures, the Sigma 24-35mm f/2 Art Lens shows only a minor amount of flare even with a clear-sky sun in the corner of the frame. That amount of flare increases as the aperture narrows (this is normal) until a noticeable amount of flare is present at f/16.

The 24-35 Art shows a moderate amount of barrel distortion at the wide end. This distortion transitions into no distortion in the mid focal lengths and continues to transition into mild pincushion distortion at the long end.

This lens features a 9-rounded-blade aperture design. Nine blades, being an odd (vs. even) number, will create 18-point stars from specular highlights when stopped down significantly (try f/16). The bokeh (background blur quality) appears OK, but not remarkable.
As an “HSM” lens, the Sigma 24-35mm f/2 Art Lens gets Sigma’s best Hypersonic Motor-driven AF system. Auto focusing is quick, quiet and internal. This lens does not change size with focusing (or zooming) and the front filter threads do not rotate. FTM (Full Time Manual) focusing is supported. Simply change the focus ring to adjust focus, even with the camera powered off.
I spend a lot of time testing AF accuracy beyond using the standard calibration tool and, in most instances, found the 24-35 Art to deliver the same consistently accurate results. There were, however, a small handful of result sets that were somewhat troubling. In those scenarios, shot-to-shot variance was higher than I expected. As with all lenses, confirm that the 24-35 Art’s AF system works well with your camera body before putting to serious use.
As one would expect from a lens projecting a larger image circle, the full frame lens is modestly wider than the APS-C format lens. While I did not tear these lenses down to compare internals, it is obvious that the exterior design characteristics are heavily shared.
The Sigma 24-35mm f/2 DG HSM Art Lens has very smooth, perfectly-damped and ideally-sized zoom and focus rings that have no play in them. Also very nice is the rear-position zoom ring design choice. The zoom ring only rotates a short 38°, but … that rotation amount matches the short focal length range nicely.
This lens does not feature weather sealing. Extra precautions should be taken if photographing in potentially wet or dusty situations.”

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