This page walks through the process of getting a lens to focus accurately on the Nikon D850, in the field and in a way that can be applied most anywhere without needing special targets. It shows before (“out of the box”) and what a huge difference it can make to use the AF fine-tune feature, that is, transforming an unusable blurred image to a beautifully crisp one by adjusting the autofocus offset.
Two samples of the 45-megapixel Nikon D850 have shown a flange focal distance error with my Zeiss lenses that might be related to two Nikon AF lenses being so far off as to deliver unusable images out of the box—the 105/1.4E and the 14-24/2.8G. That such extreme adjustments are offered (-20 to +20) appears to implicitly acknowledge a build tolerance range that is highly variable. Indeed my 14-24/2.8G needed +20 to focus properly—the extreme end of the range.
I love the image quality of the D850, but the sloppy build tolerances are distressing. I may defer purchasing a D850 until Nikon gives me an answer on what the heck is going on—I’ve asked and I await an answer (the D850 I have is on loan). I do not know if I’ll get an answer—my experience on a number of occasions tells me that companies prefer to stonewall on issues like this, but I’ll given Nikon the benefit of the doubt for now.
I’d like to see just one (1) Nikon D850 that has a proper flange focal distance, that is, one that focuses my Zeiss lenses just like my D810 (which in turn matched the D800E and D800). I’d also like to see perfect sensor-mount parallelism, because either the D850 I have now is skewed like the previous one, or the Nikon 105/1.4E is skewed (or both).