johnf3f said:
Your experience with the D810 mirrors this reviewer's experience:
"Although the D810 inherits much of its AF system from Nikon's pro-sports D4S...
Despite being formally rated to -2EV (only one stop less than the Nikon D750), in real-world use, we were surprised to find the D810 failing more often than it should in low light. As part of the Sony a7R II review we compared the performance of the Nikon D750, Canon EOS 5DS and the Sony in extreme low light. The D810 simply couldn't keep up in this company. It even falls well behind its predecessor, the D800/E, which we found to focus down to -3 to -4 EV in our lab (it was under-rated)...
The D810's center point gave up at around -1 EV, while the D750 hovered around -2.5 EV* (-3 EV for a high-contrast cross-hair target, though), and the Canon DSLRs performed best: focusing down to nearly -3 EV. The Canon's also felt more confident at locking focus, likely a testament to their dual cross-type design that 'searches' for detail along four axes using f/2.8 and brighter lenses. Next, we look at off-center performance...
Again, the D810 remains substantially behind its competition, with the Nikon D750 pulling ahead of all the other cameras in this test. The 7D Mark II falls slightly behind the performance of its lower-light-rated center AF point, only focusing down to roughly -2 EV.
Does this translate to real-world usage? Yes: when out shooting, we found the D810's autofocus will give up in very low light circumstances, particularly when there's little contrast for it to pick up on. While these circumstances may be rare for your type of shooting, we found it to be a nuisance at dim wedding receptions, or romantic candle-lit dinners, particularly considering we didn't have these issues with a Canon 5DS/R, nor a Sony a7R II as long as we had an F1.4 lens attached to it. Furthermore, quite often we found focus to be quite far off (back or front-focused) in low light, despite meticulous calibration under daylight - we can't help but wonder if accuracy (and/or precision) also suffers under low light."
- http://www.dpreview.com/reviews/nikon-d810/8
I believe all these issues are ironed out in the D750, D500 and D5. In fact, DPReview considers D500 AF to be class-leading:
"Autofocus is the D500's great strength: along with the D5 it's the best we've ever used. Just as mirrorless cameras appear to be closing the gap when it comes to following simple subjects, the D500 comes and blows them (and its DSLR rivals) all out of the water. It's not just a question of the mirrorless-esque across-the-frame AF coverage or of the number of cross-type focus points, it's this plus some of the best subject tracking we've seen and the fine-grained customization that allows the behavior to be tailored to shoot a wide range of different sports."
- http://www.dpreview.com/reviews/nikon-d500/12
It's interesting to note that DPReview did not review the D810 until 2 years after its release and never once mentioned the AF deficiencies of the D4/D4s. The D810 only got reviewed after Nikon got their act together and released the 'class leading' D500/D5. Well, that's DPReview for you.
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