This is a continuation of a series of posts on the Nikon D850. The series starts here. You should be able to find all the posts about that camera in the Category List on the right sidebar, below the Articles widget. There’s a drop-down menu there that you can use to get to all the posts in this series; just look for “D850”.
This post is only tangentially about the D850. In the previous post, it looked like the D850’s PDAF system was not compensating for focus shift in the Nikon 105/1.4 lens. I asked Marianne Oelund, who is the expert on Nikon AF (and a lot of other things) what she thought. She said that it is possible that focus shift compensation was dropped in the transition from the D810 to the D850. Since I haven’t gotten rid of my D810 — yet — I thought I’d try the same test as yesterday, with the same lens on the D810.
Here are the FocusTune plots.
And at f/5.6:
The -4 adjustment samples at f/1.4 are outliers, and I’m mentally taking them out. It’s impossible to say whether one AF compensation step on the D810 is more-or-less equivalent to one such step on the D850, but I will still note that the shift in the D810 as the lens is stopped down is about 6 units in the negative direction (with the -4 samples ignored, more if they’re not). The shift for the D850 was about 10 units in the same direction. I wouldn’t put too much stock in the quantitative difference, but there is a significant shift in the same direction.
I’m thinking that there is not a huge difference in the way the two cameras are performing here.
One thing to note is that the spread of the points at each adjustment value is, if anything, a bit worse with the D810, so there’s no reason to think that the D850’s disappointing PDAF repeatability with the 105/1.4 wide open is new behavior. Another thing to consider is that the 105/1.4 is a new lens, and maybe the D810 doesn’t know about it.