Longitudinal Chromatic Aberration and focus shift
Although the Nikon Z 24-120mm f4 S has a focal ratios of only f4.0 I tested for longitudinal color aberrations (loCA, a.k.a. “axial color” or “bokeh CA”). These 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 shows very little loCA. At 24mm focal length there’s a slight trace of focus shift towards the background – which becomes sharper faster than the foreground.
The following shot shows that the Nikon Z 24-120mm f4 S produces almost no coloration around high-contrast edges in the focus plane or around background subjects:
Sharpness and contrast
Let’s have a look at the theoretical performance of the Nikon Z 24-120mm f4 S, Nikon AF-S 24-120mm f4G VR and Nikon Z 24-200mm f4-6.3 VR:
These MTF charts show the computed lens-performance of lenses wide open at infinity without influence of diffraction at 10 line-pairs/mm (red) and 30 lp/mm (blue). Higher values are better (more contrast) and the closer the dotted and solid lines are together the less contrast dependents on the orientation of the test-pattern (less astigmatism). 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 on a 45MP Nikon Z7 camera.
From the charts the new Z 24-120mm f4 S should be clearly sharper than its predecessor. But compared to the Nikon Z 24-200mm f4-6.3 VR the new lens seems not so far ahead.
Let’s see how this theoretical performance translates into real life results in the sharpness test based on Siemens-stars shot on a 45MP Nikon Z7. Processing was done in Lightroom 11.1/CRAW 14.1 from RAW to Adobe Color profile with the built-in lens profile for CA, vignette control and distortion 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 other lenses by clicking on the crops of the respective focal length.
Nikon’s new zoom lens performs very well up to 50mm focal length – even delivering quite good resolution in the FX-corner. Zooming in beyond 50mm makes the DX- and FF-corner become progressively softer. The test also showed that field curvature is practically negligible up to 50mm but becomes relevant at longer focal lengths where I had to refocus for each crop in a row.
The following 100% crops for each focal length show the Nikon Z 24-120mm f4 S from f4.0 down to f11 compared to the Nikon AF-S 24-120mm f4G VR, Nikon Z 24-70mm f4 S, and Nikon Z 24-200mm f4-6.3. Images from the F-Nikkor were developed without Adobe’s lens profile as Lightroom claimed that it already applied the integrated lens profile for correcting distortions. But this is obviously not the case as you can clearly see in the FX-crops of the F-Nikkor below.
If you want to see all the details and comparisons read on. Or you can fast-forward to the performance at long distances.
Performance at 24mm:
Performance at 28mm:
Performance at 35mm:
Performance at 50mm:
Performance at 70mm:
Performance at 120mm:
The Nikon Z 24-120mm f4 S is clearly sharper than its F-mount predecessor at any focal length and across the full-frame. Comparing the new lens with the Z 24-70mm f4 S also shows the Z 24-120 in the lead up to 50mm focal length – but not by the same margin as against the F-Nikkor. The Z 24-200 is mostly softer than the Z 24-120 in the FX-corner but the center is comparable with the DX-corner of both lenses pretty close: the Z 24-120 being sharper at the short end, the Z24-200 sharper at the long end. Stopping the Z 24-120 down to f5.6 or f8 improves acuity of the corners especially at focal lengths of 70mm or longer.
Performance at long distances
The Siemens-star test-targets are shot at a distance of 45x focal length (i.e. at around 5m for 120mm focal length). But performance of lenses also depends on the shooting distance. Therefore I present another series of images shot on a 45MP Nikon Z 7 of a city around 1 km away. Processing was done in Lightroom 11.1/CRAW 14.1 from RAW to Adobe Color profile with the built-in lens profile compensating CA and vignetting. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. All shots were made from a heavy tripod with image stabilization switched off. As usual I have selected the diagonal that provided the better corner results as almost any lens is a bit decentered.
The following images show the complete scene wide open plus 100% crops from the center, DX-corner, and FX-corner shot with the Nikon Z 24-120mm f4 S. For comparison I shot the Nikon AF-S 24-120mm f4G VR within minutes of each other. You can access the large originals but please respect our copyright and only use those images for personal use.
The Nikon Z 24-120mm f4 S repeats its good results from the previous test and – again – clearly outperforms it’s F-mount predecessor. The softening of the DX- and FX-corner at focal lengths of 75mm or longer is not as clearly visible as in the synthetic test as the dismal weather did not provide a very contrasty scene.
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 Nikon Z 24-120mm f4 S from f4.0 to f8.0 at 24mm and 120mm focal length. All images were developed to the same brightness in the center and are shown with vignette control Off (1st row) resp. Normal (2nd row):
With vignette control set to Normal vignetting is relatively mild even wide open both at the short and long end of the lens. From f5.6 onward it is practically irrelevant. With vignette control set to normal the extreme corners are lifted at f4.0 only about 0.35 EV at 24mm and 0.5 EV at 120mm. Adobe’s RAW converter automatically applies vignette control as it was set in camera – but you cannot alter the setting in postprocessing.
Auto distortion control cannot be disabled in camera nor in Adobe’s RAW converter. That’s the same as with Nikon’s Z 24-200mm f4-6.3 VR and Z 24-70mm f4 S. Nikon’s lens profile at least does a pretty good job to correct for distortions – in the view-finder, for JPGs out of camera or RAWs developed in Adobe software:
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 Nikon Z 24-120mm f4 S at different apertures compared to the Nikon AF-S 24-120mm f4G VR:
The Nikon Z 24-120mm f4 S produces very little coma even wide open. The test also shows no color artifacts around bright streetlights. This is clearly better than from the F-Nikkor.
The next 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 crops below the main image are from the center, DX-corner, and FX-corner resized to make them comparable across all my reviews.
The diameter of the Bokeh balls in the center is determined by the entrance pupil of the lens. So both the Z-Nikkor and the F-Nikkor produce Bokeh balls of equal size. Comparing the other qualities of the circles of confusion between both lenses shows the Z-Nikkor to have a smoother inner structure and less outlining than the F-Nikkor. Both lenses compress the circle towards the FX-corner pretty strongly: Even at f8.0 the clipping is still visible.
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.
All four lenses suffer from their meagre focal ratio and produce Bokehs that are not very satisfying. The Z 24-70 and Z 24-200 producing the least blur. Between the Z 24-120 and the F-Nikkor it’s hard to chose: The Z 24-120 seems to be a bit less nervous in the background but has less blur in the foreground.
Looking at another crop (now at 100%) from the same images showing the ruler shows a slight tendency of the Z 24-120 for double contours.
The Nikon Z 24-120mm f4 S achieves a pretty decent maximum magnification of around 1:2.4 in close-up shooting at 120mm focal length. The area of sharp focus is just 58 x 87mm. The images shown below were shot at a magnification of around 1:2.5 and the crops are from 1mm, 11mm, and 18mm off the center of the sensor respectively..
The Nikon Z 24-120mm f4 S produces quite sharp results in the center even wide open. But the image softens pretty quickly outside the center and even stopping down to f16 did not yield the sharpest results. Field curvature plays a role here but is not the only reason for the soft performance.
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 Nikon’s Z 24-120mm f4 S for these artifacts I went through a series of well calculated shots against a strong light source to provoke glare and ghosting. The lens hood was mounted in all shots. 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:
On the short end the Nikon Z 24-120mm f4 S is quite resilient against flare, ghosting and veiling glare. So the blacks really stay deep black even against strong contra light. Zooming in produces more ghosting and flare but the artifacts are still not overly disturbing. This is much better than what the Nikon AF-S 24-120mm f4G VR produces like this at 24mm or that at 70mm.
The lens produces nice sunstars at the wide end if you stop down to f11 as you can see above. But at f5.6 and f8 they are not very prominent:
Next check out my sample images!Check prices on the Nikon Z 24-120mm f4 S at B&H, Adorama, WEX UK or Calumet.de. Alternatively get yourself a copy of my In Camera book or treat me to a coffee! Thanks!