FWIW, I'm mostly still stuck in the past and a Nikon D5 is my primary camera(depending on the situation, I could claim any number of different cameras a backups, including a D4 and D850). At this point the D5 is nearing the decade old mark.
Maybe it's a matter of not knowing what I'm missing, but I really don't find the D5 AF to be especially lacking. When I compare it with my Fuji X-T5, my only entry into the mirrorless world, I do miss full-frame focusing. In general, though, the D5 is excellent at initial subject acquisition and with tracking. BTW, I don't do wildlife, but these days I'm often photographing kids, which can be even more wild and unpredictable in movement!
I know Fuji isn't known to be the best out there for mirrorless AF, so it's probably not a great basis for comparison and at this point it's a few years old...although it's one of the few cameras I've not only bought new but also bought when it was a current model. I think it was released November or so 2022, and I bought mine May 2025. I actually bought new because used ones were selling for close to new prices, and because once I'd decided on Fuji(I wanted a SMALL mirrorless camera to complement my DSLRs, and at the time they absolutely had the best line-up of APS-C lenses-Nikon announced a few great additions the week my X-T5 was delivered) I decided that the X-T5 checked more boxes for me than any older Fuji offering out there.
In any case, I should probably update the firmware on my X-T5, but mine shipped with 1.x and 2.0 dropped while I was on vacation with the camera, and sometimes fighting it left, right, and center. 2.0 actually fixed a lot of issues and improved AF performance dramatically. In fact my biggest complaints about the camera's AF come down to initial subject acquisition being easily "fooled" in certain situations, and tracking doing the same. In fact at times it will get distracted and drop a moving subject in a situation where my D5 would most certainly have held.
At the end of the day, though, with both cameras, as well as my backups(the D850 has the same basic AF system as the D5, just not as fast or decisive, the D4 is good but a generation older) my in-focus hit rate is very high. I also get a very high hit rate with my Pentax 645n and its straight out of the 1980s AF. The absolute best thing you can do with ANY camera is practice with it. Use it in non-critical situations or just take it out knowing that you're learning to use the thing. Henri Cartier-Bresson had a tradition of "breaking in" a new camera or lens by photographing geese at a local park-there's actually a lot to be said for using a new piece of equipment in a familiar situation.
At this point, as much as I always love new gear, I actually have no compelling reason to upgrade any of my bodies. If I bought something now, it would either be a second D5 or possibly a D6. I could make an argument for either.
Oh, BTW, I'm interested to see where global shutters go. Nikon's D1 series cameras actually had true global shutters and I'm not sure many people at the time even realized it. They looked and sounded like they had a mechanical shutter curtain, but it was only a single curtain that would "fan" up and down over the sensor and I believe was mostly used for flash sync. I've used D1 series cameras to measure flash duration, especially on studio flashes, because it syncs at any speed up to 1/16000 or however fast it goes. These cameras using a CCD are a large part of the "why" it works, but low resolution(2-6mp) certainly helps also.
Maybe it's a matter of not knowing what I'm missing, but I really don't find the D5 AF to be especially lacking. When I compare it with my Fuji X-T5, my only entry into the mirrorless world, I do miss full-frame focusing. In general, though, the D5 is excellent at initial subject acquisition and with tracking. BTW, I don't do wildlife, but these days I'm often photographing kids, which can be even more wild and unpredictable in movement!
I know Fuji isn't known to be the best out there for mirrorless AF, so it's probably not a great basis for comparison and at this point it's a few years old...although it's one of the few cameras I've not only bought new but also bought when it was a current model. I think it was released November or so 2022, and I bought mine May 2025. I actually bought new because used ones were selling for close to new prices, and because once I'd decided on Fuji(I wanted a SMALL mirrorless camera to complement my DSLRs, and at the time they absolutely had the best line-up of APS-C lenses-Nikon announced a few great additions the week my X-T5 was delivered) I decided that the X-T5 checked more boxes for me than any older Fuji offering out there.
In any case, I should probably update the firmware on my X-T5, but mine shipped with 1.x and 2.0 dropped while I was on vacation with the camera, and sometimes fighting it left, right, and center. 2.0 actually fixed a lot of issues and improved AF performance dramatically. In fact my biggest complaints about the camera's AF come down to initial subject acquisition being easily "fooled" in certain situations, and tracking doing the same. In fact at times it will get distracted and drop a moving subject in a situation where my D5 would most certainly have held.
At the end of the day, though, with both cameras, as well as my backups(the D850 has the same basic AF system as the D5, just not as fast or decisive, the D4 is good but a generation older) my in-focus hit rate is very high. I also get a very high hit rate with my Pentax 645n and its straight out of the 1980s AF. The absolute best thing you can do with ANY camera is practice with it. Use it in non-critical situations or just take it out knowing that you're learning to use the thing. Henri Cartier-Bresson had a tradition of "breaking in" a new camera or lens by photographing geese at a local park-there's actually a lot to be said for using a new piece of equipment in a familiar situation.
At this point, as much as I always love new gear, I actually have no compelling reason to upgrade any of my bodies. If I bought something now, it would either be a second D5 or possibly a D6. I could make an argument for either.
Oh, BTW, I'm interested to see where global shutters go. Nikon's D1 series cameras actually had true global shutters and I'm not sure many people at the time even realized it. They looked and sounded like they had a mechanical shutter curtain, but it was only a single curtain that would "fan" up and down over the sensor and I believe was mostly used for flash sync. I've used D1 series cameras to measure flash duration, especially on studio flashes, because it syncs at any speed up to 1/16000 or however fast it goes. These cameras using a CCD are a large part of the "why" it works, but low resolution(2-6mp) certainly helps also.
