This has nothing to do with skimping.
It depends on how Nikon wants to position the Z6 III and there are serious disadvantages that go hand in hand with a sensor that has such a slow read-out as that of the A7IV.
Rolling Shutter, the whole E-Shutter experience gets f.... up with such a slow read out, lossless compressed only 5-6 FPS max, 10 FPS only compressed RAW or jpeg, movie performance...
I think Nikon is doing everything right by focusing on performance and speed with the Z6 III, the advantages should clearly outweigh the small gain in resolution for the majority.
Just as Canon ultimately did with the R6 II.
If you want more resolution, go straight for the Z8, Z9, or be patient until Nikon presents a Z7 II successor.
However, gimping a Z6 III in terms of read out speed to the level of the previous Gen, as would be the case with the sensor of the A7IV, would definitely be the wrong way to go.
Especially as the Z6 III tends to be the next generation compared to an A7IV, where an A7V will probably be the competitor in the foreseeable future, alongside the R6 II.
All valid points.
Canon upped their MP count in part due to poor receipt of their initial 20mp R6 offering… certainly not enough for me, but half the influencers out there tried to convince themselves and us that it didn’t make a huge difference… that depends on the user. 24 is not enough for me now on FF. 26mp on ASPC (Fuji) can be as getting out to 1200mm on ASPC is not that challenging.
My hope for a higher MP Sensor for the Z6iii is two-fold, one (selfishly) I would like it, and most likely won’t leave my A7IV for less, secondly, it would future proof the platform better and draw newer users. Especially in light of an A7V which likely will have more than 30mp’s simply because it’s often Sony’s modus operandi. New users could care less of “high ISO performance”, “slow readout”, or “rolling shutter”… they have no idea what it even means. They see “24mp” vs. “30mp”, etc. Of course if Nikon can still keep the $2000 price-point… that did have a big impact on why I bought the Z6II vs. the A7IV initially, it was the lack of glass and poor AF that had my finally trade it for the Sony.
Nikon is doing well, but did not make the top 3 for sales in Japan this year (with ZF sales, that may change for next year).
Both the Z8 and Z9 are phenomenal products, but also both larger than the Z6II, Z7, A7IV, A1, R5, R6ii, all Fuji’s etc. I’m are large guy with a background with large DSLR’s and I would rather not have that large a body now, especially with the size of most Nikon glass (Plus they are $$$$).
The direction Nikon goes will certainly be dependent on who/what their intended target wants. For me as a mostly stills shooter, Hybrid specs are not such a big factor, nor is rolling shutter even. With 6 kids and all our activity and sports related shooting, the 30mp slower readout of the A7iv sensor does everything I need, but I am a Prosumer not a Pro… which seems to be a large segment of the $2k-$2.5k market at the moment.
I wish there were a camera with 40mp, 20mp crop mode, Canon’s menus, Sony’s glass eco-system and customization, Nikon’s build, ergs, and color science, etc. etc.

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Amazing to have such choices today. I was revisiting all my D200 photos from Glacier NP last weekend and though 12mp was just fine then, I may have to try enhancing the resolution on a few.
There is less and less uniquely compelling about the Sony eco-system with 3rd Party glass expanding to Z, Godox now available for Z, etc. Nikon needs to nail this particular camera, it’s similar to what the Civic is to Honda and fewer people are going to jump into a Z8/9. I thought the ZF was pure genius on Nikon’s part. Show the world they are hip and test out the Z6III AF System simultaneously.