Monday, January 20, 2014

Sigma 24-105mm f/4 DG OS HSM ART Review

Sigma 24-105mm f/4.0 DG OS HSM A on Canon EOS 6D

It's hard to talk about Sigma's new 24-105mm "standard-zoom-plus" lens without also mentioning Canon's ubiquitous EF 24-105mm IS L. Canon's multipurpose full frame standard zoom is everywhere thanks to frequent bundling with their full frame cameras. There's virtually no point to buying the Canon 24-105L by itself as it costs so much less when bundled, and because there are so many good quality used copies available on the secondary market. However, there is palpable interest in having a better lens in this in this focal range, as neither the Canon nor the Nikon 24-120VR seem to set photographer's pulses racing. 

Into this mix comes the Sigma 24-105mm f/4 DG OS HSM "A." Ever since the introduction of the 35mm f/1.4 ART, Sigma's lenses have had increasing expectations heaped upon them, and this lens is no different. Given the both Canon and Nikon are competent (even good lenses), can Sigma move the bar towards the "stellar" and "excellent" end of the spectrum?

Build and Design

 

The new Sigma is quite a heafty lens and is actually heavier than its Canon counterpart. The build quality is in keeping with the refreshed Global Vision lineup: the finish is a deep glassly black, the zoom dial has a nice damped feel to its operation and there is barely any wobble with the lens extended. The focus ring, however is absurdly thin, which probably betrays how often Sigma thinks users will manually focus this lens. The placement of the focus ring is inwards of zoom ring, which is the oposite of the Canon but similar to the Nikon 24-104VR.

Sigma 24-105 and Canon 24-105
Sigma and Canon lenses extended


Like the Nikon (and unlike the Canon), the zoom barrel is a double-sleeve construction and extends quite a bit from its base. Fully extended, the Sigma 24-105mm bears an unexpected resemblance to its crop-sensor cousin, the 17-70mm "C." Actually, this shouldn't be a surprise, as the 17-70mm lens  on a crop sensor camera covers roughly the same focal length and equivalent aperture range (27-105mm at f/4-f/5.6 equiv). Note the inconsistency in naming: both lenses do essentially the same thing for their respective formats, but the crop lens is designated at the lower "C" level, whereas the 24-105mm gets the "A" designation. Then again, the Canon 24-105mm is an "L" lens, and the Nikon 24-120VR is a "Gold Ring" lens, so small wonder that Sigma chose to market on an equal footing with the mainline manufacturers.

Sigma 24-105 and Nikon 24-120
Sigma and Canon lenses extended

The optical formula  is quite modern (i.e., sophisticated): 19 elements in 14 groups. There are two fluorite-glass elements, two low-dispersion elements and two aspherical elements. Like its competitors, this lens is stabilized. Sigma claims four stops of image-stabilizing power from the OS system; in practice that would be a stretch, but between two and three stops seems reasonable. Autofocus operation is fast and silent. 
 

Zoom Range


The following images were shot on a Canon EOS 5D Mark III, JPEG's are out of camera. Shot at f/4 through the focal range, images look like this:

24mm
50mm

75mm

105mm

As you can see, it's an extremely versatile lens, and will be able to cover everything between landscapes and fairly serious portrait work. A maximum aperture of f/4 may not sound very fast, but bear in mind that on a full frame camera, this is the equivalent of a "fast" f/2.8 on a crop sensor camera.

There's visible barrel distortion at 24mm, which becomes slight pincushion at the long end of the zoom. The distortion seems to be a bit more than the Canon 24-105L, but not out of keeping with many lenses of this type. You'd be hard pressed to tell the difference from 35mm onward between these two lenses. For all intents and purposes, from approximately 35mm to 80mm, the Sigma is more or less distortion free

Chromatic aberration and ghosting are hard to demonstrate in the limits of the ad hoc impromptu test method, but subjectively, the Sigma is roughly e in-between the Canon and the Nikon, with the Canon being the best of the three.

Aperture Range


The following is the aperture range shot at 75mm. (For reference, the figurine is approximately 10cm (or 4 inches) high. Note that in the f/4 shot, and throughout the above images, there is obvious vignetting (dark corners) throughout the zoom range. This is also a trait shared by the Canon 24-105L and the Nikon 24-120VR, but the Sigma seems worse at it. You can still make out the vignetting at f/5.6, and it isn't until f/8 that it disappears completely.
 
f/4

f/5.6
f/8
f/11

If you refer to the objective testing done by others on the web, the Sigma actually performs slightly better than either the Canon or the Nikon in terms of outright resolving power. The difference isn't much, but it bears repeating that these are out of camera JPEG's, which haven't been enhanced in post processing. This isn't bad for a lens that exceeds the maxim that a quality lens doesn't have more than a 3x zoom ratio. Though the little Chinese figurine is not a good subject to demonstrate outright detail resolving, there is a pleasing quality to the broader global contrast that this lens produces. Lenses of this type tend to be sharper at the wide end of the zoom range, and that is more or less what you see. Fully extended to 105mm, the lens looses a bit of its bite, but center resolution remains good.

Like almost all recent Sigma lenses, the bokeh is pleasing and does not demonstrate much in the way of harsh fringing or "nervousness."

Closing Thoughts


From a purely objective standpoint, this is an excellent lens. It's not better than the Canon or Nikon lenses in all attributes, but it is better in enough ways for most people to consider this a superior lens...but not by much. Compared to the Nikon 24-120mm f/4G ED V, the Sigma makes a strong case; better resolution, better chromatic aberration control, lower price. As a competitor to Nikon's kit Nikkor 24-85mm f/3.5-4.5G ED VR lens for the D610, the Sigma is more expensive, but you get more lens as well.

Against the Canon, the Sigma faces a tougher problem. Because of the discount that the 24-105L lens has when bundled with a 5D or 5DmIII, the "list" cost of the lens by itself is practically a farce. It would be a brave choice to skip the kit and elect for the body-only option and then adding the Sigma 24-105mm, as that would add significantly to the total cost for only a modest gain in image quality.

There's one final group to consider, and that is crop sensor users of either Canon or Nikon persuasion who would be tempted to get this as a general-purpose lens that can one day be mounted on a full frame camera. The good thing about this is that the optics will be good enough for whatever full frame camera that the user eventually steps into. On a crop camera, the issues of corners (vignetting, aberrations, resolution loss, etc.) becomes irrelevant. The downside is the size and heft of this lens; on a 70D or a D7100 it's not exactly casual walk around material. 

However, judged on its merits alone, the 24-105mm f/4.0 DG OS HSM ART is an excellent lens, and shows that Sigma has been serious about improving their offerings with their refreshed lineup of lenses.



With thanks to Broadway Camera.

3 comments:

  1. I'm not sure how much it effects IQ but it's worth noting that the Nikon 24-120 is longer than the Canon or Sigma.

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    Replies
    1. Agree, Patto.
      While 15 extra mm at the long end doesn't mean as much as on the wide end, it's still 15mm neither Canon nor Sigma lenses have.

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    2. You get a little more compression, and a little better bokeh at 120mm vs 105mm. Yes, more is more, but in may be the deciding factor or it may not be. For example, if you already have ART lenses and a dock, then the Sigma is as good choice. However, if you are looking at the D750, then the kit bundle is a no-brainer.

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