The Nikon Z6II, Nikon Z7II, and Nikon Z8 Compared
The following is the first of a multi-part series of posts comparing the night sky performance of various cameras and lenses. In this post I will compare images of the Milky Way made with a Nikon Z6II, Nikon Z7II, and a Nikon Z8 using a Nikon 20mm f/1.8 Z lens. I have always been curious about which camera might yield the best results. The lower resolution 24MP Nikon Z6II has a reputation for being excellent for low light photography, while the higher resolution Nikon Z7II and Nikon Z8 at 45.7MP are theoretically considered better for larger prints and for when heavier cropping is desired.
All of the images in this evaluation were untracked and taken from a single fixed position on a tripod with a 5s delay to minimize potential of camera shake. The white balance (WB) for each camera was set to “Daylight” making it the default as-shot setting when the raw NEF files were imported into Capture One. All images were exported to jpg files directly from the original Nikon raw NEF files from Capture One. No editing other than cropping where noted was done in order to make for easier direct comparisons. Each image can be enlarged by left-clicking to get a better view. Once enlarged, double clicking zooms in closer.
The first set of images shown below in figure 1 were each taken with exposure times of 20s at ISO 6400 at an aperture of f/2.8 on a Nikon 20mm f/1.8 Z lens. In this case the 20s exposure time was chosen by applying the so-called “400 Rule”, which is simply 400 divided by the focal length of 20mm to get the recommended exposure time in seconds.
Figure 1 – Milky Way shots at 20s, ISO6400, with Nikon 20mm f/1.8 Z lens at f/2.8.
In the above images, there are some very subtle color and exposure differences but otherwise they all look strikingly similar. Even a small amount of post-processing work would easily make them virtually indistinguishable.
Below in figure 2 are the same images cropped to approximately 6:1 to show closer-in detail. At this level it is easier to compare relative noise performance. The Nikon Z6II image would be a 3.2″ crop from the full 20.16″ image while the Nikon Z7II and Z8 is a 4.4″ crop from a 27.52″ image.
Figure 2 – Enlarged center Milky Way from figure 1.
Once again, the differences are indeed minor. Under much closer inspection, the Z6II arguably shows some slightly better color detail likely due to its comparatively better noise performance at ISO6400 over the Z7II and Z8. However, owing to the lower resolution of the Z6II, the noise also appears a bit more granular.
I would also say that the Z7II does look a little bit cleaner than the Z8. That is, I believe, likely due to the performance of its BSI sensor compared to the faster and reportedly slightly noisier stacked sensor of the Z8. Regardless, all of the differences appear to be rather modest and can only be seen by zooming in and comparing side-by-side.
The next set of images shown below in figure 3 are the same as those in figure 1 except that they were done at f/2.0 at ISO3200. Exposure time is the same at 20s.
Figure 3 – Milky Way shots at 20s, ISO3200, with Nikon 20mm f/1.8 Z lens at f/2.0
Similar to the case in Figure 1, all images look quite similar excepting some minor color and exposure differences. Notably, these images shot at one stop more aperture and half the ISO compared to those of figure 1 are slightly darker. Comparing the noise levels of these images shot at ISO3200 to the previous ones shot at ISO6400 does show some improvement but not significantly so.
In figure 4 below are crops of figure 3 to show more detail in the Milky Way center. The crop is approximately 6:1. Similar to the case of figure 2 above, I don’t see much difference except that the Nikon Z6II shows a little more detail compared to either the Z7II or Z8. Once again, the Z7II also appears a bit cleaner than the Z8. Still, the differences are pretty slight and mostly only visible under significant magnification.
Figure 4 – Enlarged center Milky Way from figure 3.
Finally, below in Figure 5 are shots done with the Nikon Z7II comparing 20s vs 10s exposure times. The image on the left is from above which is 20s exposure time, ISO6400, at an aperture of f/2.8. On the right is 10s exposure time, ISO6400, at an aperture of f/2.0. In this case the difference is quite noticeable. Star trailing is much less leading to an overall cleaner looking image.
Figure 5 – Nikon Z7II shot at 20s, ISO6400, f/2.8 (Left) and Nikon Z7II shot at 10s ISO6400, f/2.0 (Right)
In conclusion, the images shot with the Nikon Z6II, Z7II, and Z8 all appear to be quite similar. The difference between ISO3200 and ISO6400 is also not all that significant. The biggest beneficial effect, short of stacking or tracking exposures, is reducing exposure time. In this case from 20s to 10s. Naturally, that is where faster lenses are most beneficial to bring in more light. In this case the Nikon 20mm f/1.8 Z lens is an excellent choice as, not only is it fairly fast, but it also has excellent performance wide open. Many fast, wide lenses may not offer such benefit, however, if they have poor sharpness or exhibit significant errors such as coma.
As far as which camera performs the best is not especially obvious. As observed earlier, only under high magnifications are any minor differences possible to see. Such differences are thus not overly relevant as they simply cannot be seen under normal viewing conditions. If I had to choose just one for untracked or unstacked imaging it would likely be the Nikon Z6II. It does show slightly better noise performance and, more importantly, produces smaller files to work with than either the Z7II or the Z8. For tracked or stacked imaging, I might prefer the Nikon Z7II as it would give me the most resolution in noise reduced images. Either way, all of the above cameras produce similar and excellent results.