Review Sigma 24-105 mm f/4 Art (C FF)

8 December 2013

To the surprise of many, in October 2013 the Sigma 24-105 mm f/4 Art lens, suitable for an APS-C and a full-frame camera, was announced. We hadn’t expected that. The 24-105 mm zoom is a popular zoom lens among Canon photographers, due to the broadly useful zoom range and because it’s sold as a kit lens with various Canon full-frame SLR cameras. Some portrait photographers prefer a 24-105 mm zoom lens to a 24-70 mm, because that model at a focal length of 105 mm gives a bit more flattering portrayal if you make a full-screen portrait. At 24-105 mm, this is a bit more universal than a 24-70 mm zoom. It’s possible that may have been a consideration for Sigma in bringing out this lens.

Sigma 24-105 mm f/4 DG OS HSM Art @ Canon 5D MK3

On a camera with a full-frame sensor a 24-105 mm zoom lens is the universal walk around zoom, which can replace the popular fixed focal lengths of 24 mm, 28 mm, 35 mm, 50 mm and 85 mm. The Sigma 24-105 mm Art lens comes with a pouch and a flower-shaped lens hood.

Construction

The Art series lenses are so solidly built that they withstand comparison with the best professional lenses. If you put the Canon 24-105 mm f/4 L next to the Sigma 24-105 mm, the Sigma looks more modern. You also notice that the Sigma lenses looks more professional, and is more heavily built. The lens is not affected by creeping (shifting of the zoom when the lens hangs vertically, which our Canon test model did suffer from) and both the zoom ring and the focus ring are much better padded. The Sigma is also heavier, larger and has a larger filter size than the Canon.
The heavy brass mount fits perfectly and completely without play on the camera. It may seem exaggerated to pay attention to it, but with the high resolution of modern cameras the quality of the mount is also becoming increasingly important.
This lens is made with attention to detail. I find the “in/out” text on the supplied lens hood to be a funny detail, so that you know which direction you have to turn it to tighten or loosen the lens hood.

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Auto focus

The lens is equipped with two switches: image stabilization on/off and auto focus/manual focus. These switches have a – hand-painted – white background, allowing you to better see the current setting of the switch.
The HSM drive of the auto focus is fast and can be overruled manually at any time if you want to adjust the focus point.

Image Stabilization

We tested the image stabilization (OS) at a focal length of 105 mm. The image stabilization turned out to be not only very quiet, but also effective. The Imatest measurements showed that a picture taken by hand at a shutter speed of 1/200 was slightly less sharp than a picture made at a shutter speed of 1/25 second using the built-in image stabilization. Move your mouse over the image on the right. That’s actually a profit of 3 stops, and that’s very good.

At shutter speeds slower than 1/25 the images are no longer razor-sharp. Even so, I could still get reasonably sharp pictures at a shutter speed of 1/3 second and a focal length of 105 mm. Below you’ll see a 100% cut-out of the picture shown here. Without image stabilization, the result doesn’t bear looking at.
Tip: Both with and without image stabilization, it’s true that at the point where the sharpness begins to decline through motion blur, the variation in the sharpness is relatively large. If at slow shutter speeds, you make multiple pictures right after each other, then the chances are great that there will be a sharp picture among them.

Tip: Zowel met als zonder beeldstabilisatie geldt dat op het punt waar de scherpte begint af te nemen door bewegingsonscherpte, de variatie in de scherpte relatief groot is. Maak bij lange sluitertijdenmeerdere opnames vlak achter elkaar. De kans is groot dat er toch nog een scherpe opname tussen zit.

Resolution

The optical design consists of 19 elements in 14 groups, and includes several high-quality glass types, such as two elements of a glass type (FLD) with the same properties as fluorite, two SLD lenses and 3 aspherical lenses.
The chart on the right shows the results from our Imatest measurements of in-camera jpg files. At multiple focal lengths, the corner sharpness is somewhat lower than the center sharpness. That’s common for a good lens on a camera with a full frame sensor. At focal lengths of less than 85 mm, the resolution in the center never drops below 2500 lines per picture height. At the longest focal lengths, we measure relatively speaking the lowest resolution, but the center resolution remains above 200 lines per picture height. All very good, then.

Across the board, the Sigma 24-105 mm rated comparable to, just a little bit better than, the Canon 24-105 mm that we reviewed earlier. In our overview of results at individual focal lengths, you can compare the sharpness of the Sigma 24-105 mm with the Canon 24-105 mm.
To give you an impression of the difference in sharpness between the Sigma 24-105 mm f/4 and the Canon 24-105 mm f/4, you see below a 100% cutout from a picture made at 105 mm f/4, with both lenses focused at precisely the same point. In the center, it’s hard to see a clear difference in sharpness, but in the corners, it’s clearly visible. Even so, in the vast majority of cases you won’t see any difference in sharpness in practice.

Vignetting

We start from “What you see is what you get” and therefore use 1 scale to assess the vignetting of all lenses, regardless of the sensor size. Lenses tested on a camera with a full frame sensor have much more trouble with vignetting. This also applies to the Sigma 24-105 mm Art. At maximum aperture, the vignetting in the corners at multiple focal lengths is up to 2 stops. You will really need to correct vignetting.

Distortion

Across virtually the entire range, distortion is visible. At 24 mm the visible distortion is barrel-shaped. From 30 mm, the visible distortion is pincushion-shaped. Distortion is quite correctable with lens correction profiles in Photoshop or Lightroom. However, during the test these profiles were not yet available.

Bokeh Sigma 24-105 mm f/4 Art

Many photographers who use a camera with a full frame sensor find me the bokeh important. The diaphragm of the Sigma 24-105 mm Art is composed of 9 rounded blades, which deliver a quiet background blur. With our bokeh test setup, the pictures made with the Canon 24-105 mm L gives a more restless bokeh than the Sigma 24-105 m f/4. The bokeh shows clear circles with the Canon; the Sigma, practically none.

Also in the pictures taken in practice the bokeh of the Sigma 24-105 mm is more beautiful. But, you get a nicer bokeh if you use a brighter lens.

Click on the image on the right.

From the MTF charts that manufacturers place on their website, you can distill an indication of the quality of the bokeh. The smaller the difference between the horizontal and vertical resolution (sagittal and meridional MTF), the quieter the bokeh. On the Global Vision site of Sigma, there are various charts for Sigma 24-105 mm Art performance data for MTF, distortion and vignetting. If we compare that with the MTF charts for the Canon 24-105 mm, then you would be able to see a confirmation of our observation that the bokeh of the Sigma at 105 mm is a bit nicer.

Move your mouse over the image for a comparison of the Sigma 24-105 mm f/4 Art with the Canon EF 24-105 mm f/4 L

Flare Sigma 24-105 mm f/4 Art

Like the other recent lenses from Sigma, this lens is well protected against flare. Ghosts such as those found in the Lenstip review we didn’t come across. Even if you are shooting straight into the sun, the flare zone is limited. It’s just a very good result.

Chromatic aberration Sigma 24-105 mm f/4 Art

At this point, we had hoped for more for a lens from the Art series, because most Sigma lenses have a design in which you encounter very little chromatic aberration. There are also several glass elements of high-quality glass types applied, which have little CA or correct for CA. In the RAW pictures we found – at large magnifications – visible lateral chromatic aberration in the form of purple and green edges at sharp contrast transitions in the corners of the image, also in practice pictures of branches against a gray sky. Fortunately, chromatic aberration in RAW files is also easy to correct with software.

In the jpg files, the lateral chromatic aberration was considerably better corrected. In our measurement results, we saw a kind of dip, where the CA in the corners was higher for both large and small apertures. The CA was always low; at f/5.6, the CA was the lowest.

Conclusion Sigma 24-105 mm f/4 Art review

Use the Lens Comparison or look in our list of reviewed lenses to compare this lens with other lenses.

WYSIWYG score: More and more often when designing a lens, distortion, color separation and vignetting are consciously not optimally corrected. As a result, fewer expensive lens elements or exotic glass types need to be used, which ultimately results in a more attractive selling price. The lens manufacturer relies on automatic correction of these characteristics in the camera or in photo editing software. The “jpg-score” gives you for a lens/test camera combination, “What you see is what you get” when all available lens corrections are applied in the camera.

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Pure RAW score: With more expensive lenses, a manufacturer often goes to great lengths in the lens design to prevent lens errors. Neither costs nor effort are spared, which can be recognized by the use of exotic types of glass and many lens elements. The “RAW score” approximates the intrinsic quality of the combination of lens and test camera, with CameraStuffReview attempting to bypass any automatic lens corrections of RAW files. If you use lens correction profiles in Photoshop or Lightroom to convert RAW files, the RAW scores for distortion, vignetting and chromatic aberration will be higher or equal to the corresponding jpg scores.

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Pros

Cons

Universal zoom lens for full frame with good image quality
Good image stabilization
Little flare, no ghosts
Build quality of the highest level
AF tuning with USB dock possible
Mount conversion (for an additional fee) possible

Visible distortion and vignetting
Visible CA in RAW files

The Sigma 24-105 mm f/4 Art in image quality does as well as the Canon EF 24-105 mm L. The Sigma Art wins on points over the professional Canon L lens. At the longest focal lengths, the sharpness of the Sigma is higher and the bokeh is a bit higher than the Canon. Distortion and vignetting are both clearly visible and are best corrected in Photsohop or Lightroom. At the time of this test, the lens correction profiles for Photoshop and Lightroom were not yet available, but in general the correction profiles for Sigma lenses are very good. The differences in image quality are so small that we think that image quality is no reason to switch. The Sigma 24-105 mm Art not only looks more modern and more distinguished, in terms of build quality, this lens beats the Canon EF 24-105 mm L.

The Sigma 24-105 mm f/4 was released as part of the Art series. The equivalent of the Sigma 24-105 mm f/4 for a camera with an APS-C sensor is the Sigma 17-70 mm Contemporary. I wouldn’t have found it nuts had the Sigma 24-105 mm been released in the Contemporary series. On the other hand, if you consider the Art series to be the successor to the EX series, then it’s not illogical to bring out the Sigma 24-105 mm f/4 in the Art series. And the Canon EF 24-105 mm L, released in the professional L-series, in our test results has met its better in the Sigma 24-105 mm.

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