Now that I have almost three weeks experience with the Z9 and am home reading what others are writing, I think we need some clarification of a number of comments I've seen.
- Can't tell when camera's photographing — The Sony A1 has a similar problem when set to silence. No one's figured out the best possible "I took a shot" indicator yet. However, the Z9 has three different choices, one of which is "blackout." The viewfinder doesn't actually black out, but it imposes a very brief darkening between frames. It's impossible not to know the camera is photographing with this setting enabled.
- Nikkors focus more slowly — Pretty sure this isn't a lens issue, if it is an issue at all. Nikon cameras have always had a bit of a hesitation to obtain initial focus (compared to Canon in DSLRs, and Sony in mirrorless). But they snap to focus fine once they have figured out what they are doing. I'd tend to say the Z9 has less hesitancy than any previous Nikon, but I need to perform more tests to verify that. Moreover, you can help the system by making wise autofocus choices. Leaving "all subjects" enabled seems to hesitate a bit more than choosing the proper subject. But when I say hesitate, I'm talking about something that happens so fast that it can't reliably be measured. Microseconds.
- Sony's AF sensors update faster — Probably true, but not the right thing to assess. The Z9's focus sensor updates, while much faster than the Z6 II and Z7 II, still aren't 100% accurate to what the camera is doing. I'm going to have to do a side-by-side battle on this one to very, but here's my initial assessment: The Sony A1's focus sensors update faster but the camera doesn't necessary focus dead-on in some cases. The Nikon Z9's focus sensors actually sometimes lie to you because they lag slightly, but the focus is dead-on. I prefer the Z9 to the A1 in this respect.
- The speed of a bird flying is a key determinate of focus performance — No, not really. We've long had focus systems that could keep up with even peregrine falcons flying full speed. The real issue with tracking fast moving birds has much more to do with how well you can keep the bird framed to what the focus system is looking for. It's one reason why VR (IS in Canon-speak) was such a big thing. What the Z9 does is compensate (some) for poor camera/lens handling. That's particularly true with birds against sky, where if you're using Auto-area AF with Animal subject detect the camera will track the bird well over about 80-90% of the frame.
