- Ed Dozier
Nikon Z9: Un-retire Your Lenses
I have a few Nikkor “F-mount” lenses that I recently started using again. Why did I stop using them in the first place? In a word: focus. The Nikon Z9 has the best focus capabilities of any camera I have ever tried, and it is now giving new life to lenses that have frustrated me since I first got them.
Nikon Z9 and Nikkor 85mm f/1.4 AF-S
The first lens I un-retired is my Nikkor 85mm f/1.4 AF-S. I had virtually stopped using this lens because of an optical effect called spherical aberration. For many (most?) high-speed lenses, they will shift focus when you change the lens aperture. You can only focus-calibrate a lens at a single aperture setting, which isn’t a problem for most lenses, but it sure is for this 85mm. Every aperture change, up through about f/5.6, would shift the focus and generally ruin the shot. I calibrated my lens at f/1.4, but every shot at a different aperture would be soft. Very irritating.
DSLRs focus with the lens aperture wide-open, and then stop the lens down an instant before taking the shot. Therein lies the problem: automatically shifting the focus before taking the shot. The Z9 will focus at the requested aperture (through f/5.6), and totally avoid the problem of spherical aberration.
It’s of course possible to always shoot a DSLR using contrast-detect at the requested aperture, as long as you don’t mind super slow focus and trying to see the rear screen out in the sunshine. I happen to mind. Also, DSLRs aren’t as good at accurate contrast-detect focusing as you might think.
All of my DSLRs operate on the principle of “good enough” for focus. After they get within a small tolerance of correct focus, they simply stop. This is especially true of phase-detect focus. Most users are happy with the focus results, but my resolution-measuring software shows just how loose and variable this good-enough approach is. I can rarely get peak resolution readings by using either phase-detect or contrast-detect focus on a DSLR; I have to manually shift focus by small amounts to get the highest resolution results (one out of a ton of shots), or else pick the best results out of a bunch of auto-focus attempts.
I have tried experiments with my Nikon Z9, and have found that the resolution-measurements are typically repeatable within an MTF50 contrast variation of 1 or 2 lp/mm! This is just extraordinary.
There’s one more reason that I have started using my 85mm f/1.4 lens again: it now has vibration reduction. The Nikon Z9 includes in-body image stabilization (IBIS), so now the 85mm (that has no VR) can suddenly take advantage of stabilization! Just wonderful.
Z9 with Nikkor 24-70 f/2.8 VR
Another ‘F’ lens that has been taken out of semi-retirement is my 24-70 f/2.8 VR. This lens is notorious for shifting focus as you zoom it. I would focus-calibrate it at 70mm, and find that 24mm (and most other focal lengths) was terrible when shot wide-open. No matter which focal length I would choose for focus-calibration, the other focal lengths were always soft. My Sigma lenses can be calibrated at multiple focal lengths to solve issues like this, but not Nikon lenses.
The Nikon Z9 with its super high-speed Expeed 7 processor just nails focus. Zooming no longer has an impact on focus calibration. As a matter of fact, the Nikon Z9 needs NO focus calibration with any of my lenses, even though it still offers a focus-calibration feature.
You have to use the FTZ-ii adapter with these lenses, of course, but focus speed isn’t impacted at all. The increase in weight is trivial, and I honestly don’t even notice the adapter while I’m shooting.
I have a friend that has un-retired his F-mount Nikkor 70-200 f/2.8 lens since he got his Z9. That lens also suffered from severe focus shift while zooming, which drove him crazy. He reports that it now works perfectly on his Z9. Now he’s considering retiring his D850 and D500 cameras and getting a second Z9.
I already wrote some articles (for example) on lenses with different mounts that can be adapted to the ‘Z’ mount. These are manual-focus lenses, but the great focus-peaking found on the Z9 has now given these lenses new life (including vibration reduction), as well.
I don’t feel any pressure to get Z-mount lenses, since my F-mount lenses perform better than they ever have. My Z9 has nearly paid for itself by letting me use lenses that had been largely abandoned. It’s just a bummer that my screw-drive auto-focus lenses won’t work on the Z9.