Testing: Longitudinal Chromatic Aberration and focus shift
Lenses with focal ratios of f4.0 or slower normally don’t show longitudinal color aberrations (loCA, a.k.a. “axial color” or “bokeh CA”). These would show up as magenta coloration in the foreground and greenish hues in the background and are not easily corrected in post-processing. The Sony is no exception with the only coloration in the test shots below from color moiré.
There’s also no focus shift to speak of.
Sharpness and contrast
Let’s have a look at the theoretical performance of the Sony FE 12-24mm f4.0 G first and compare it to the Sigma 14-24mm f2.8 DG DN Art, and Sony FE 12-24mm f2.8 GM:
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.
When comparing these charts keep in mind that the Sony FE 12-24mm f4.0 G is show here at f4.0 while the other two lenses are at a more challenging f2.8. That said the Sony f4.0 G definitely looks softer at the short end than the Sigma and Sony f2.8 GM. At 24mm focal length the Sony FE 12-24mm f2.8 GM looks best while the Sony f4.0 G seems to be better than the Sigma up to 10mm image height but then dropping off to soft full-frame corners.
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.
Sony’s zoom lens looks very sharp in the center throughout the zoom-range and and has a pretty good FF-corner from 14-20mm focal length. The APS-C-corner is not bad but suffers from astigmatism. It’s actually a little disappointing compared to the very good the center and solid performance in the FF-corner. The lens also exhibits some field curvature.
Following are all the details and comparisons with the Sigma 14-24mm f2.8 DG DN Art. I expect to add comparisons with the Sony FE 12-24mm f2.8 GM soon. So be prepared for a great amount of eye-watering details, or fast-forward to the performance at long distances.
Performance at 12mm:
At 12mm the Sony f4.0 G show its best performance at f5.6 with the FF-corner already softening at f8.0 and even more so at f11. Seems like diffraction is more acute with the light coming in at an extreme angle.
Performance at 14mm:
At 14mm, f4.0 the Sigma DN is sharper than the Sony FE 12-24mm f4.0 G across the sensor with the difference at the APS-C-corner the most obvious. Stopping the Sony f4.0 G down beyond f5.6 again softens the FF-corner visibly.
Performance at 17mm:
While the center of the Sony f4.0 G and the Sigma DN look very close the Sigma DN produces the sharper images further off-center. 17mm also seems to be the focal length where the diffraction penalty in the FF-corner from stopping down beyond f5.6 returns to “normal”.
Performance at 20mm:
Similar story at 20mm focal length with the center of the Sigma DN now a tiny bit softer than from the Sony f4.0 G.
Performance at 24mm:
At 24mm the Sigma DN at f4.0 is even sharper across the full frame than the Sony f4.0 G at f5.6.
In this comparison the Sony FE 12-24mm f4.0 G zoom lens is mostly outperformed by the Sigma 14-24mm f2.8 DG DN Art.
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.
The long-distance test confirms the results from the preceding test: the zoom lens is very sharp in the center (with a bit of haloing/blooming around bright areas at 24mm) but softer at the APS-C-corner. The FF-corner is very usable at the long end but soft at 14mm.
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 Sony FE 12-24mm f4.0 G down to f11. For comparison I use the Sigma 14-24mm f2.8 DG DN Art shot only minutes apart. 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 12mm:
In this test the FF-corner sharpens up nicely until f8.0. But then it starts much softer than in the previous test where focus was optimized for each crop. A consequence of field curvature.
Results at 14mm:
At 14mm the Sony f4.0 G and the Sigma DN look almost indistinguishable in the APS-C image circle. But the Sigma clearly produces the sharper FF-corner.
Results at 17mm:
Out side the center the Sigma DN is clearly sharper than the Sony f4.0 G.
Results at 20mm:
Same again as at 17mm focal length.
Results at 24mm:
The Sony f4.0 G is now suffering a bit from blooming in the center at f4.0. A flaw which the Sigma DN also shows at f2.8. But stopping the Sigma DN down to f4.0 gets rid of this effect and makes it clearly sharper than the Sony f4.0 G across the full frame.
The long-distance test has the FF-corner of the Sony FE 12-24mm f4.0 G suffer from field curvature which together with the slightly softer APS-C-corner makes it less sharp across the full frame than the Sigma 14-24mm f2.8 DG DN Art. And its otherwise very good center performance is adversely affected at 24mm focal length from a bit of blooming at high contrast edges.
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 at f4.0, f5.6, and f8.0. 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 12mm vignetting is strong at f4.0 and still very visible f8.0. The lens profile though reduces this to acceptable levels by lifting the extreme corners by about 1EV at f4.0 and +0.9EV at f5.6. But at f8.0 the lens profile simply does not lift corner brightness at all which leads to vignetting at f8.0 being much stronger than at f5.6 – when vignette control is set to Auto. This happens with JPGs straight out of camera and RAW files developed in Lightroom. But I don’t see the effect in my long-distance test-shots (also done with vignette control set to Auto), perhaps it’s just a freak blip on my test-radar. At 24mm vignetting is much milder to begin with so the strange effect isn’t as obvious as at 12mm. Btw.: 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 12mm focal length which are not fully corrected by the lens-profile(s) 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 lens shows a bit of coma at f4.0 at the short and the long end – but nothing to worry about.
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 Sony FE 12-24mm f4.0 G is first, followed by the Sigma 14-24mm f2.8 DG DN Art. Crops are from near the center, APS-C-corner, and FF-corner resized to make them comparable across all my reviews.
The Sony FE 12-24mm f4.0 G produces the clearly smaller Bokeh balls as its entrance pupil is 40% smaller than from the Sigma DN or Sony f2.8 GM. The Sony f4.0 G also has quite prominent outlining plus another onion ring inside which all makes for a busy Bokeh ball. But the Sigma DN is not entirely free of these effects either. But both lenses show very little cat’s eye effect towards the corner.
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 produces a much stronger blur outside the plane of sharpest focus. But looking at another crop (now at 100%) from the same image showing the ruler reveals that the the Sony f4.0 G suffers less from double contours on fine structures near the plane of sharpest focus than the Sigma 14-24mm f2.8 DG DN Art.
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 Sony FE 12-24mm f4.0 G 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 Sony FE 12-24mm f4.0 G produces a few ghosting artifacts and flares but overall contrast is pretty high with deep blacks – not bad, but the Sigma 14-24mm f2.8 DG DN Art is better still. And there’s quite a flare which 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 Sony FE 12-24mm f4 G at Amazon, B&H, Adorama, or Wex. Alternatively get yourself a copy of my In Camera book or treat me to a coffee! Thanks!