Testing: Longitudinal Chromatic Aberration and focus shift
Lenses with focal ratios of f2.8 or larger are often prone to longitudinal color aberrations (loCA, a.k.a. “axial color” or “bokeh CA”). These normally show up as magenta coloration in the foreground and greenish hues in the background and are not easily corrected in post-processing. The Sigma has almost no loCA. Very good!
There’s also no focus shift to speak of although at 24mm the background becomes sharper faster than the foreground.
Sharpness and contrast
Let’s have a look at the theoretical performance of the Sigma 14-24mm f2.8 DG DN Art first and compare it to the Sigma 14-24mm f2.8 HSM Art, Sony FE 12-24mm f2.8 GM, and Sony FE 12-24mm f4.0 G:
These MTF charts show the computed lens-performance of lenses wide open without influence of diffraction at 10 line-pairs/mm (red) and 30 lp/mm (green) except for the charts of the Sony FE 12-24mm f4.0 G where the red lines show the performance at f8.0. Higher values are better (more contrast) and the closer the dotted and solid lines are together the less astigmatism (= resolution depends on the orientation of the test-pattern) the lens has. The x-axis displays the distance from the optical axis (=center of the sensor) in mm. I’ll show you the real-life performance at 4 mm (center), 13 mm (APS-C/ APS-C-corner), and 20 mm (FF/FF-corner) on a 42MP Sony A7R II camera.
On the short end the new optical construction has lifted resolution and contrast of the zoom lens considerably compared to its DSLR sibling and it also looks better than both Sonys. The long end is a different story though: Up to 10mm image height the Sigma 14-24mm f2.8 DG DN Art produces less contrast at fine structures than the other lenses – albeit with very little astigmatism.
Let’s see how this theoretical performance translates into real life results in the sharpness test based on Siemens-stars. Processing was done in Lightroom 10.0/CRAW 13.0 from RAW to Adobe Color profile with the built-in lens profile for Vignette Control and CA compensation applied. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. White-balance was adjusted to a neutral white and I did some exposure compensation to make the brightness of all crops match. So you will not see light fall-off in the corners.
The following are all 100% crops!
First up is an overview of the wide-open performance at different focal lengths. You can jump to the detailed results at different apertures and comparisons with the alternatives by clicking on the crops of the respective focal length.
Sigma’s zoom lens looks very sharp in the APS-C image circle throughout the zoom-range and shows only a slight softening towards the FF-corner. The lens also exhibits very little field curvature over its zoom range. Very good!
Following are all the details and comparisons with the Sigma 14-24mm f2.8 HSM Art (shot on a 45MP Nikon D850) and Sony FE 12-24mm f4.0 G. I also included comparisons with Nikon’s Z 14-24mm f2.8 S (shot on a 45MP Nikon Z7) as Sigma surely is working hard on offering its newest mirrorless lenses for Canon RF and Nikon Z mount too in the future. And I expect to add comparisons with the Sony FE 12-24mm f2.8 GM soon. So be prepared for a huge amount of eye-watering details, or fast-forward to the performance at long distances.
Performance at 14mm:
At 14mm, f2.8 the Sigma DN is sharpest in the APS-C image-circle with the FF-corner looking pretty similar between the Sigma DN, Sigma HSM and Z-Nikkor. At f4.0 the Sony FE 12-24mm f4.0 G looks comparable to the Sigma DN in the center and the FF-corner but softer in the APS-C-corner.
Performance at 17mm:
At 17/18mm the Sigma HSM clearly falls back outside the center while the Sigma DN and Nikon Z are neck-and-neck with the Sigma DN having a slightly sharper APS-C-corner and a bit softer FF-corner than the Z-Nikkor. Stopping down to f4.0 increases acuity of the Sigma DN in the FF-corner visibly and it beats the Sony f4.0 G outside the center.
Performance at 20mm:
Similar story at 20mm focal length with the Z-Nikkor now clearly softer outside the center than the Sigma DN.
Performance at 24mm:
At 24mm we see similar results as at 20mm: The Sigma DN rules the competition – except for the center of the Z-Nikkor.
In this comparison the Sigma 14-24mm f2.8 DG DN Art zoom lens shows that it’s at the top of its game. Sigma may have given up a tiny bit of center sharpness at the longer focal lengths to achieve this but I rather like the overall result.
Performance at long distances
The Siemens-star test-targets are shot at a distance of 45x focal length (i.e. at around 1.1m for 24mm focal length). But performance of lenses also depends on the shooting distance. Therefore I present another series of test-shots of a city around 1 km away on a 42MP Sony A7R II. Processing was done in Lightroom 10.0/CRAW 13.0 from RAW to Adobe Color profile with the built-in lens profile compensating vignetting and CA. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. I used manual focus at the largest aperture and did not change focus for other apertures. All shots were made at ISO 100 and image stabilization switched off.
Following is an overview of the wide-open performance at different focal lengths. You can jump to the detailed results at different apertures and comparisons with other lenses by clicking on the crops of the respective focal length. As usual I have selected the diagonal that provided the better corner results as almost any lens is a bit decentered.
In this long-distance test the zoom lens looks (again) very good right into the extreme corners of a high resolution full-frame sensor. Only at 24mm focal length the center shows a bit of haloing/blooming around bright areas reducing contrast a bit.
If you want to see all the details and comparisons read on. Or fast-forward to the next chapter on vignetting and distortions.
The main image shows the complete scene wide open to give you an impression of the angle of view and to judge vignetting. Following the main image are 100% crops from the center, APS-C-corner, and FF-corner for each focal length from the Sigma 14-24mm f2.8 DG DN Art down to f11. For comparison I use the Sony FE 12-24mm f4.0 G shot only minutes apart. Plus the Sigma 14-24mm f2.8 HSM Art shot on a 45MP Nikon D850 and Nikon Z 14-24mm f2.8 S on a 45MP Nikon Z7 on different days. But you can still compare resolution of fine details quite well. And I’ll add comparisons with the Sony FE 12-24mm f2.8 GM soon.
You can access the large originals but please respect our copyright and only use those images for personal use.
Results at 14mm:
The Sigma HSM and Sony f4.0 G clearly have the softer FF-corner compared to the Sigma DN and Nikon Z.
Results at 17mm:
The FF-corner of the Sigma HSM has now caught up but its APS-C-corner is softer than from the Sigma DN and Nikon Z. The Sony f4.0 G again has the softest FF-corner.
Results at 20mm:
Similar results as at 17mm focal length.
Results at 24mm:
The Sigma DN and Sony f4.0 G are now suffering a bit from blooming in the center which makes both the Sigma HSM and Nikon Z render crisper details. But outside the center the Sigma DN produces the sharpest image.
In this long-distance test comes out ahead of the other lenses with the exception of center performance at 24mm focal length: High contrast edges suffer a bit from blooming.
Vignetting and distortions
To make it easier to see light fall-off in the corners of a full-frame sensor I’ve arranged a series of three shots each with the Sigma at f2.8, f4.0, and f5.6. All images were developed to the same brightness in the center and are shown with vignette control Off (1st row) resp. Auto (2nd row):
At 14mm vignetting is strong at f2.8 and still very visible f5.6. The lens profile though reduces this to acceptable levels by lifting the extreme corners by about 1EV at f2.8. At 24mm vignetting is visible at f2.8 but unobtrusive when stopped down or corrected via lens profile. Adobe’s RAW converter automatically applies vignette control as it was set in camera – but you cannot alter the setting in postprocessing.
The setting for distortion control in camera is completely ignored by Adobe’s RAW converter and treated as Off. So you have to activate the profile that comes with the Adobe software manually to get rid of the distortions when developing RAW files. Just be aware though that activating Adobe’s lens profile also adds another lift in corner brightness – which can be reduced manually. Distortions are of a mustachioed barrel type at 14mm focal length and turn to slight pin-cushion at 24mm (see below).
Rendering of point-light sources at night-shots
Night-shots pose a different challenge for lenses as the contrast is even higher than under bright sun and point-light sources can reveal some weaknesses such as coma, haloing and colour-aberrations that do not show up as prominently in other test-shots. The 100% crops below the main image show the effect of coma in the FF-corner at various apertures:
The Sigma DN shows very little coma at the short and the long end.
Rendering of out-of-focus point-light sources
This test is for the rendering of point-light sources in an out-of-focus background. The circle of confusion that is produced by this test is pretty indicative of Bokeh performance (in the background) and light fall-off. Ideally the out-of-focus image of the point-light is evenly lit and perfectly circular, with no “onion-rings”, and without coloration. Large aperture lenses normally produce an effect known as “cat’s eye” the further away from the optical axis the point-light is projected. This is due to optical vignetting in the lens barrel when light enters the lens from an angle.
The Sigma 14-24mm f2.8 DG DN Art is first, followed by the Sony FE 12-24mm f4.0 G. Crops are from near the center, APS-C-corner, and FF-corner resized to make them comparable across all my reviews.
The Sigma DN produces the clearly larger Bokeh balls as its entrance pupil is 40% larger than from the Sony f4.0 G. The Sigma also has the smoother interior and less outlining compared to the Sony. And its cat’s eye effect is almost non-existent.
Now let’s see how this analysis of out-of-focus point-light sources translates into Bokeh-performance shooting a book-shelf. Crops are from the foreground, middle-ground, and background resized to make them comparable across all my reviews.
The Sony f4.0 G clearly suffers from its lowly f4.0 focal ratio in this comparison. The Sigma DN and Nikon Z look best in this comparison perhaps with a slight advantage of the Sigma in the background. Looking at another crop (now at 100%) from the same image showing the ruler reveals that the Sigma 14-24mm f2.8 DG DN Art produces less double contours / outlining on fine structures near the plane of sharpest focus than the Sigma HSM or Nikon Z. The least obtrusive in this respect is the Sony f4.0 G.
Flare, ghosting, and sunstars
Catching a strong light-source shining directly into the lens is always a risky business: it could produce strange colorful ghost-images or reduce contrast considerably through flare and glare. The appearance of flare and ghosting depends on factors like the aperture and the angle of the light hitting the lens. So to judge the proclivity of the Sigma 14-24mm f2.8 DG DN Art for these artifacts I went through a series of well calculated shots against a strong light source to provoke glare and ghosting. Following are two typical example results. The little bright square inset in the upper left shows the respective area with an exposure compensation of +3 EV to make it easier to see which levels of black the lens renders at that point:
The Sigma 14-24mm f2.8 DG DN Art produces some muted ghosting artifacts and flares but overall contrast is very high with deep blacks – clearly better than from the Sony FE 12-24mm f4.0 G. There’s only a mild flare from the upper right corner which only occurs at a very narrow angle when the light-source is just outside the corner. Stop down to f11 to get well defined sunstars at 14mm. At 24mm focal length (and f11) the sunstars are a bit less spikey.
Next check out my sample images!Check prices on the Sigma 14-24mm f2.8 DG DN Art at Amazon, B&H, Adorama, Wex, or Calumet.de. Alternatively get yourself a copy of my In Camera book or treat me to a coffee! Thanks!