Thom Hogan

Both Nikon and Sony use a lot of similar and overlapping sensor technology. The Nikon and Sony sensor initiatives have intertwined pretty much since the late 1990's (maybe even before). A number of things we take for granted in Sony Semiconductor's image sensors first appeared in Nikon cameras (column ADC, phase detect on sensor, dual gain, etc.). In some cases, Nikon was doing the development work, in some cases Nikon worked with a third-party who had interesting technology (e.g. Aptina, who eventually licensed dual gain and on-sensor PD to Sony). 

So it probably won't surprise you if I say that the differences in the Nikon Z and Sony A systems really don't tend to revolve around the image sensor itself (the A7 Mark IV's 33mp and A7R Mark V's 61mp sensors notwithstanding; they just have more pixels using the same technologies). Both Nikon and Sony have their own small twists around the basic Exmor sensor technologies, and in cases like the Z6 II versus A7 Mark III, for instance, there's virtually nothing that separates them on an image sensor level.

Even with Sony pushing more pixels than Nikon lately, I'm not sure that actually is providing the advantage that some think it is. The full well capacity of the A7R Mark IV is about 34k electrons, while the full well capacity of the Z7 II/Z9 is more like 60k electrons. Someone maximizing the exposures on both cameras should find the Nikon approach has some advantages in high contrast situations, even though the dynamic range numbers might look the same from a lot of sources.

So let's get one thing out of the way quickly: image quality from a comparable Nikon and Sony mirrorless camera probably isn't something you should be basing your decision making on. Sure, Nikon's EXPEED has a different set of JPEG look defaults than Sony's BIONZ, but both cameras pretty much allow you to customize JPEGs to look as you'd like them to. Sony's raw files are far larger than Nikon's, which is an annoyance, but at the highest settings again I'd not say that you should be basing your camera buying decision on image sensor if you're a raw shooter.

No, the tangible differences between the Nikon Z cameras and the Sony A cameras that most people will have a clear reaction to are two:

• Ergonomics
• Focusing

Let's start with ergonomics, which I take to mean how the camera feels and handles, button placements and controls, the menu system, whether you can easily change settings with your eye still at the viewfinder, how well touch controls are implemented, and so on. 

Nikon has a long history with button+dial control that dates back to the N8008 film SLR in the 1980's. Nikon also has a long history of Italian-designed body/control size and positioning, which dates back to the F4 film SLR, also in the 1980's. While Nikon has tweaked both things over the years, a Nikon body today, DSLR or mirrorless, is recognizable to any long-time Nikon user. There's little learning curve in switching from any Nikon SLR or DSLR to a Z mirrorless camera.

You can't really say the same for Sony. While there are still some bones and appendages that can be traced back into the Minolta film SLR era, Sony has been much more experimental and inconsistent in ergonomics. The original Sony mirrorless cameras, the NEX models, featured an entirely different, very consumerish menu and control system (which even had two personalities). That was changed several times before we got to the current Sony approach. But even with the A9-derived changes to body grip plus button position and findability, Sony still has some catching up to do: on all but the latest cameras menus are scattered and often use opaque wording, the Sony LCD touch system still isn't complete (except on the A1, A7 Mark IV, and A7R Mark V), and it often feels like Sony isn't paying as much attention to things that don't show up in spec sheets as Nikon is. 

Autofocusing is also an area where Nikon and Sony have somewhat different approaches. I can't really say that one is better than the other, though. They're different. 

I will say that Sony had a slightly better all-automatic (no user control or interaction) autofocus approach than Nikon until the Z9 appeared, which will appeal to those that don't want to take the time to learn the nuances of how autofocus actually works (note dpreview's "In many cases, you'll find you just don't have to mess with your autofocus settings again" in their A9 Mark II review; that applies to many current Sony cameras, as well, but really only the Nikon Z9 would likely get a similar statement). 

While things have improved over time, I still feel that the Sony cameras have a tendency with objects in motion to get "real close to where focus should be" rather than actually nail the focus plane. If you look at that dpreview A9 Mark II review and look at the performance on their "weave" test you'll see what I mean. Pay very close attention to the eyes. Notice how they snapped into high acuity in shot 14, but they were just okay in the others? That's what I mean by "close to focus but not always in focus." Still, that's often better performance than most consumers and even many enthusiasts achieved with their SLRs and DSLRs, so Sony users tend to be happy. Moreover, the Sony A1 improved on that. I'd argue that the lower priced Nikon Z's do a better job of precision focus than the lower priced Sony cameras, but only if you take a bit of control back from the system and understand how to use that control. 

I don't say the things in the previous paragraph lightly. I've used many Sony and now Nikon mirrorless in wildlife and sports shooting regularly for the last few years, often side by side. These types of photography are sort of worst-case for autofocus systems, particularly small birds in flight (BIF) and sports like basketball where the motion can be erratic. I see more slight focus misses—misses many less critical users might not call a miss at all—from the Sony mirrorless system than I do from the Nikon mirrorless system. On the other hand, if I let the camera do all the work—i.e. no user interaction with the focus system—the Sony cameras do a slightly better job than the Nikons. 

The Sony A1 and Nikon Z9 (and Canon R3) have changed things at the top end, though. Both the A1 and Z9 have arguably state-of-the-art focus systems that do an amazing job with subject recognition. Nikon's approach is different than Sony's though, with Nikon recognizing more attributes on more subjects and having a personality that tells you how it's approaching the auto recognition ("is it human, yes, then here’s the body, head, eyes, nailed it" and "oh, wasn't human, was it animal, then body, head, eyes, nailed it" and "oh it wasn't human or animal, so was it a vehicle" and so on). Sony is fixated on eyes if it sees them, then defaults to closest subject most of the time if it isn't finding eyes. 

Which brings me to a curious point: it's not the difference in what the two brands can and do achieve in autofocus that causes the biggest user reaction and response. Instead, it's the "I didn't have to learn as much with the Sony to get usable results" type of reaction that typically gets a lot of talk on the Internet. Only the Nikon Z9 gets that same level of reaction. I wouldn’t say that this type of reaction is actually accurate. Both the A1 and Z9 focus systems required learning and occasional user override to achieve best possible results.

So, at the big picture level, here are the big three things that most people react to differently with Nikon and Sony:

• Image sensor — I'd say pretty much ignore this. What differences that do exist are small and not likely to be important to you. Yes, even the 61mp versus 45mp comparison at the top of the lineup. While 61mp seems like a much bigger number than 45mp, it's actually a smallish resolution gain at the expense of other things that are often important (diffraction, noise, etc.). I had both a Z7 II (45mp) and an A7R Mark IV (61mp) in my gear closet for awhile. I used the Z7 II for more tasks than the A7R Mark IV because the Nikon's sensor produces a better balance. I ended up selling the A7R Mark IV (I  also have a an A1, so that wasn't as big a move as it seems). Yes, for landscape or architectural work, I sometimes reached for the A7R Mark IV, but that's about it.
• Ergonomics — If you're a previous Nikon user, the decision is easy: the Nikon Z system is what you should target first and foremost. Nikon simply continues to refine an already great set of handling and UI, and you'll be comfortable with a Z if you've used any Nikon DSLR, I'm pretty sure. If you're coming from a Canon, Fujifilm, Olympus, Panasonic, or other perspective, I'd say try both the Nikon and Sony systems and see which one you like best in terms of feel and control. 
• Focusing — Much like the image sensor category, there's a lot more talk about "differences" than there are tangible, meaningful differences in practice. I would tend to point the user who's just going to let the camera do it's own focusing all the time without interaction to check out the Sony system first, though (unless they can afford a Z9). But don't discount the Nikons: with current firmware and the right settings, they work quite well, as I've proven several times in Africa and in sports stadia.

I'm already hearing the loud howls from some of you. Yes, there are things that the Nikon does that the Sony doesn't, and that the Nikon doesn't do that the Sony does. But boy those tend to be very feature specific.

For instance, the Nikon cameras have focus stack shooting capabilities, the Sonys don't. But the top Sony cameras have pixel-shift shooting capabilities, and the Nikons don't. That list of feature-specific differences can get quite long. If there's a particular feature you just have to have, then what do you need my help with? ;~) Just pick the system with that feature and move on. Don't be surprised, however, if Nikon adds pixel shift and Sony adds focus stacking. The camera industry is competitive, and neither Nikon nor Sony wants the other company to have an advantage for long.

Finally, we come to model and lens choices. Sony has the clear advantage here because they've been making mirrorless systems for far longer. The lens set is more complete, and there's a fuller range of cameras. Let's look at cameras (I'm only going to discuss the current models, not the still-for-sale previous generations):

• Sony A1 versus Nikon Z9 — The Nikon Z9 is every bit the equivalent to the Sony A1, and then some, and at a lower price. 
• Sony A9 Mark II versus Nikon Z6 II — Not exactly an apples-to-apples comparison, and you give up a fair bit by opting for the Nikon in this category, particularly useful frame rate and tracking focus.
• Sony A7R Mark IV versus Nikon Z7 II — I'm going to say the Nikon Z7 II is the better well-rounded camera, the Sony A7R Mark IV the better task-specific camera (landscape, architectural). 
• Sony A7R Mark V versus Nikon Z7 II — With the latest Sony model, I’d say that Sony did indeed make the better well-rounded camera. But a Nikon Z7 III may just flip that again. 
• Sony A7S Mark III versus Nikon Z6 II — Not exactly an apples-to-apples comparison, but this is a choice you'd have if you're a videographer. The Z6 II is far closer to the A7S Mark II in video than you'd think, and better as a still camera. Of course, the A7S Mark III changed things so that it clearly favors the Sony for a true video shooter, but perhaps not by as much as you'd expect.
• Sony A7 Mark IV versus Nikon Z6 III — The previous model (Mark III) was almost exactly an apples-to-apples comparison to the Z6 II, and Nikon won the video portion of that while being a bit behind on a few still photography aspects. Now, the Z6 III has passed the A7 Mark IV in a number of areas, particularly frame rate and video capabilities. 
• Sony A6600 — No current Nikon entry. But frankly I'm not sure why I'd buy an A6600 over an A6100. Do a comparison on Sony's own site and you'll see that the differences aren't really at the major use points. You pay a lot for small performance and feature differences.
• Sony A6400 — No current Nikon entry. But frankly I'm not sure why I'd buy an A6400 over an A6100. Again do a comparison on Sony's own site and you'll see that the differences aren't really at the major points. You pay a lot for small performance, feature differences.
• Sony A6100 versus Nikon Z50 — The least apples-to-apples comparison of the bunch, though I believe Nikon and Sony are targeting the same customer with these models. Spec-wise, the A6100 is the winner, handling-wise the Z50 is better. 
• Sony A5100 versus Nikon Z30 — The A5100 went away. Good thing, too, as the Z30 is a better camera across the board.

Which brings us to lenses. As I write this:

• Crop sensor: Sony has made 22 different crop-sensor lenses and has good third-party support, particularly with the Sigma prime trio. Nikon has made three and announced two more, mostly consumer zooms; Nikon DX has some third party support at the moment; though only a handful of autofocus choices have appeared, mostly from Viltrox. The FTZ Adapter does make all the Nikon DX F-mount lenses available, though.
• Full frame: Sony has made 45 different full frame lenses and has broad third-party support, particularly enhanced by the Tamron efforts (Sony is a key investor in Tamron) as well as Sigma. Nikon has made 32 different full frame lenses. Full frame Nikon Z has modest and growing third party support. The FTZ Adapter also makes a broad range of Nikon F-mount lenses viable for Z system users. 

So a final comment goes like this: if you have a specialized need—camera or lens—you're more likely to find it in the Sony mirrorless realm at the moment. If you need is more generalized, Nikon has made a solid entry into the market that you can't ignore. Given time, Nikon will also address more specialized needs in mirrorless. For the time being, they'll rely upon F-mount lenses to help with special needs.