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 new Z-Nikkor has very little loCA and its coloration is blueish in the foreground and yellowish in the background.
There’s also no focus shift to speak of. The Nikon 24-70mm f2.8E VR shows a little more coloration (see here).
Sharpness and contrast
Let’s have a look at the theoretical performance of the new Nikon Z 24-70mm f2.8 S first and compare it to the performance of the Nikon Z 24-70mm f4.0 S and the Nikon 24-70mm f2.8E VR:
These MTF charts show the computed lens-performance of lenses wide open without influence of diffraction. Higher values are better (more contrast) and the closer the line-pairs 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/DX-corner), and 20 mm (FF/FX-corner) on a 46MP Nikon Z7 body.
From the charts the new Nikon Z 24-70mm f2.8 S should have an advantage over the Nikon 24-70mm f2.8E VR. Not so much in overall contrast (red lines) but in the fine detail where the older Nikon has a distinct drop at 10mm image height and then again towards the extreme corner of a full-frame sensor at 24mm focal length plus a generally softer rendering in the DX image-circle at 70mm focal length. Comparison between both Z zooms is a bit harder as the new lens is shown here wide open at f2.8 while the Z 24-70mm f4.0 S is at f4.0.
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 8/CRAW 11 from RAW to Adobe Color profile with the built-in lens profile applied (Vignette control=N, Diffraction compensation=OFF, Auto distortion control=ON). 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 competition by clicking on the crops of the respective focal length.
Nikon’s new zoom lens is very sharp in the DX image circle throughout the zoom-range. Only the FX-corner shows some softness over the zoom range. The lens also exhibits only very little field curvature over its zoom range (except for 24mm). Very good!
If you want to see all the details and comparisons with the Nikon Z 24-70mm f4.0 S and the Nikon 24-70mm f2.8E VR, read on. Or you can fast-forward to the performance at long distances.
The following 100% crops for each focal length show the new Nikon Z 24-70mm f2.8 S from f2.8 down to f11 compared to the Nikon 24-70mm f2.8E VR (shot on a D850 without application of a lens profile) at f2.8 and the Nikon Z 24-70mm f4.0 S at f4.0.
Performance at 24mm:
At 24mm focal length the new Z 24-70mm f2.8 S is sharper across the board than the Nikon 24-70mm f2.8E VR at f2.8 and f4.0 and it also beats the Z 24-70mm f4.0 S at f4.0.
Performance at 28mm:
At 28mm focal length Nikon’s new Z 24-70mm f2.8 S again beats the f2.8E VR and it is slightly sharper than the f4.0 S although the latter now has a markedly improved FX-corner.
Performance at 35mm:
Same story at 35mm: The new f2.8 S comes out on top.
Performance at 50mm:
At 50mm focal length the f4.0 S comes pretty close to the new f2.8 S with the f2.8E VR falling behind in the DX-corner.
Performance at 70mm:
At 70mm focal length the f2.8E VR pulls ahead in the FX-corner, but within the DX image-circle the new Nikon Z 24-70mm f2.8 S is sharper. Compared to the f4.0 S the new f2.8 S is a bit sharper in the DX-corner but comparable in the center and FX-corner.
Overall Nikon’s new Z 24-70mm f2.8 S zoom lens tops both rivals from Nikon which already performed on a very good level.
Performance at long distances
The Siemens-star test-targets are shot at a distance of 45x focal length (i.e. at around 3m for 70mm 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. Processing was done in Lightroom 8/CRAW 11 from RAW to Adobe Color profile with the lens-profile for distortion and vignetting automatically applied. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. I used autofocus at the largest aperture and did not change focus for other apertures. All shots were made at ISO 64 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 the Nikon Z 24-70mm f4.0 S and the Nikon 24-70mm f2.8E VR 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 new zoom lens looks (again) very good. The drop-off in FX-corner resolution seems only mild.
If you want to see all the details and comparisons with the Nikon Z 24-70mm f4.0 S and the Nikon 24-70mm f2.8E VR, read on. Or fast-forward to the next chapter on Rendering of point-light sources at night-shots.
The main image shows the complete scene wide open to give you an impression of the angle of view and to judge vignetting. You can access the respective shots up to f11 via the links beneath the main image. Following the main image are 100% crops for each focal length from the new Nikon Z 24-70mm f2.8 S down to f11. For comparison I use the Nikon 24-70mm f2.8E VR (on a D850 without application of a lens profile) and the Nikon Z 24-70mm f4.0 S both shot on a different day.
You can click on each image to access the large original. Please respect our copyright and only use those images for personal use.
Results at 24mm:
In comparison to the f2.8E VR the new f2.8 S looks sharper in the DX-corner while the f4.0 S almost looks indistinguishable from the f2.8 S.
Results at 28mm:
The three lenses look pretty similar when compared at the same aperture with the exception of the f2.8E R which again has a slightly softer DX-corner.
Results at 35mm:
At 35mm and f2.8 the f2.8E VR now shows an improved DX-corner which looks even a tad sharper than from the f2.8 S as does the FX-corner. At f4.0 the new Z 24-70mm f2.8 S rules the DX image-circle while the f4.0 S produces the sharpest FX-corner.
Results at 50mm:
At 50mm Nikon’s new f2.8 S zoom is the sharpest of the three lenses within the DX image-circle while the FX-corner goes to the 24-70mm f2.8E VR.
Results at 70mm:
Same story at 70mm: The DX image-circle is best from the new Z 24-70mm f2.8 S while the f2.8E VR excels in the FX-corner. The f4.0 S has also a very good center but is weaker towards the corners.
The new Nikon Z 24-70mm f2.8 S again performed very good in this long-distance test. It is mostly a bit better in the DX image-circle than the Nikon 24-70mm f2.8E VR which in turn takes the lead in the FX-corner at the longer focal lengths. Nikon’s 24-70/4.0 S competes very well in this test too up until 70mm focal length where it becomes a bit softer at the border of the DX image-circle.
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 FX-corner of the new Nikon Z 24-70mm f2.8 S, the Nikon 24-70mm f2.8E VR and the Nikon Z 24-70mm f4.0 S at various apertures:
On the short end all three zoom lenses show only little coma.
Coma at 70mm:
At 70mm focal length the new Nikon Z 24-70mm f2.8 S shows less coma than the f4.0 S but more than the f2.8E VR.
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.
All images were shot at the longest focal length and largest aperture. The new Nikon is first followed by the Nikon 24-70mm f2.8E VR and the Nikon Z 24-70mm f4.0 S.
The biggest visible difference between the lenses above is the smaller size of the Bokeh balls from the f4.0 S but that was to be expected due to its smaller focal ratio. All three lenses show mild onion rings and some outlining which has a green tinge to it on the Nikon 24-70mm f2.8E VR due to loCA. Looking towards the corners reveals some differences though: The f4.0 S shows no compression of the Bokeh balls up to 17mm image height (well outside the DX image-circle) at f4.0 while deformation of the circular shape starts already at 11mm image height with the the 24-70mm f2.8E VR which is very visible in the DX-corner even at f4.0. The new Nikon Z 24-70mm f2.8 S is somewhere in between: It shows some mild compression in the DX-corner at f2.8 but is almost circular at f4.0.
Now let’s see how this analysis of out-of-focus point-light sources translates into Bokeh-performance shooting a book-shelf.
Comparing the lenses at their longest focal length and largest aperture these test shots show a clear advantage of the new Nikon Z 24-70mm f2.8 S over the other two lenses: Foreground, background, and the transition zone (middle-ground) are much softer than from the other two lenses. The Nikon Z 24-70mm f4.0 S comes last clearly hampered by its smaller focal ratio of f4.0.
The new Z Nikkor goes down to 1:4.2 magnification which is just a little less than the f2.8 E VR and the f4.0 S. The following images were shot at 1:4.4 magnification where the area of sharp focus is just 105 x 158mm. The crops shown below are from 5mm, 12mm, and 20mm off the center of the sensor respectively:
The Z 24-70mm f2.8 S produces very usable results when stopped down to f5.6 or f8.0 similar to the Z 24-70mm f4.0 S and clearly better than the Nikon 24-70mm f2.8E VR which also fights with some focus-shift in close-up situations which makes it hard to nail focus with phase-detect AF.
Flare, ghosting, and sun-stars
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 new Nikon Z 24-70mm f2.8 S for these artifacts I went through a series of well calculated shots against a strong light source to provoke glare and ghosting.
The new Nikon Z 24-70mm f2.8 S is amazingly clear of flare and glare artifacts at the short end and at the long end it’s also very clean. And outside these artifacts the new lens renders a deep black, so there’s little veiling glare. This is a much better performance than from the Nikon 24-70mm f2.8E VR. See a comparison of both lenses at 70mm f11 where the effects are most obvious:
The little bright square inset in the upper left of both images 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. It clearly shows that the Nikon 24-70mm f2.8E VR produces more veiling glare than the new Z Nikkor. The new f2.8 S zoom lens is even a little better than the very good Nikon Z 24-70mm f4.0 S. This is not to be underestimated. After taking almost 2000 shots with Nikon’s new zoom lens I can confidently say that it copes much better with contra-light situations than the 24-70mm f2.8E VR. The latter suffers from reduced contrast quite easily even when the light source is not inside the image circle. And while you can always bring contrast back in post-processing you have already lost some shadow information in the photo that is not as easily retrievable than with Nikon’s new professional Z 24-70mm f2.8 S workhorse.
When the light-source is just outside the corner there is an obvious streak/flare at 24mm focal length. At 70mm looks more like a softer glare/halo. Fortunately this only happens in a very small area around the corners:
The new Nikon Z 24-70mm f2.8 S produces sunstars that are not very well defined although they look better than from the Z 24-70mm f4.0 S. See the following examples at f8.
Next check out my sample images!Check prices on the Nikon Z 24-70mm f2.8 S at B&H, Adorama and WEX!