I have been enjoying my A7RIII, both for resolution and high ISO performance, and was wondering how it stacks up against the 'best' high ISO-performing FF mirrorless cameras. Based on my viewing of the studio scene comparison tool, the A7s, A7III, Nikon Z6/Z6II, and Panasonic S1, and (most of all) Panasonic S1H seem to be quite good at high ISO as well. Anyone have any first-hand experience with a mirrorless camera whose ISO performance blew them away?
I wouldn't put much stock in what you see when viewing DPRs Studio Scene images on the website. Differences that look noticeable on the site simply go away if you download the RAW files and run them through DxO PhotoLab and apply DeepPRIME noise reduction.
I'm a pro event shooter who works in
really dim venues on a regular basis. I recently shot networking candids in bat-cave conditions with my a7RIII at f1.4 and ISO 25,600, and I was simply blown away by how clean and detailed this and other images were after applying DeepPRIME, even though I've been using PhotoLab (and Optics Pro before it) for many years. If you shoot a lot of high-ISO photos, investing $219 in PhotoLab 5 Elite will do far more for you than spending thousands of dollars on a new camera. And, if you're not already shooting with bright primes, consider Samyang's f1.8 primes for $300-$400 each or the 35/1.4 and 85/1.4 for right around $500 each. They're really good.
I paid just $3600 for my mint used a7RIII, 18/2.8, 24/1.8, 35/1.4 and 85/1.4 Samyang primes and PhotoLab 5, and I'd wager this combo's image quality at high ISO will utterly destroy
any other camera with a bright zoom and Lightroom, regardless of cost.

a7RIII with Samyang 85/1.4 at 1/200, f1.4, ISO 25,600, processed with DxO PhotoLab 5
Keep in mind that the JPEG file on my computer looks even a bit crisper than what you see when viewing the image here on DPR's webpage. The "100%" view on this site is also more like 150%, which makes the image look bigger and grainier than the JPEG on my computer viewed at a true 100%. It was so dark in this venue that the actual scene looked probably 1-2 stops darker to my naked eye than what you see here.
I note your small print about destroying results from any other camera "with Lightroom"
Glad you noticed my effort to be fully honest and transparent. There was nothing "small" about it. I will also note that even though DeepPRIME benefits images from all cameras, it reduces the noise differences between higher- and lower-noise cameras. The gap between my GX9 and a7III at high ISO is much less apparent post-PhotoLab. The alleged advantage of my a7III over my a7RIII is entirely unnoticeable.
But there are alternatives and of these the best is Topaz Denoise. Cheaper and you can trial it for free.
PureRAW gives you DeepPRIME and optical corrections for only $129, instead of $219 for the full PhotoLab.
And a PS. You need to learn to use it. There are a number of comparisons that show images where Topaz looks inferior. It isn't but you use them differently. You need to consider your whole work flow. If you use high iso a lot, then a full dxo workflow incorporating DeepPrime might be the way to go.
PhotoLab makes it a one-click batch operation. This is a decisive advantage for high-volume work. The old Topaz Denoise of years ago was very impressive for its time, but it required as much as 1/2 hour of manual tweaking for each image and a complicated workflow to get the best out of it. This simply wasn't practical for delivering 500 images from an awards gala, so I made do with Aperture...until Optics Pro with PRIME came along.
If you aren't shooting high iso a lot and just want to clean up shots here and there, LR or PS with Topaz DeNoise might be a better fit. The computer power you have available becomes a consideration as well.
PhotoLab runs
really well on my $999 MacBook Air with 8GB RAM.
I have used the noise reduction part of Photolab for a long time but seldom used it for editing (use Adobe CC for that). So I batch in Photolab, just mark the ones you want and apply your settings (save as a profile) and export. I export to DNG and then import those in LR.
I saw that they released the PureRAW simplified variant and thought that I would go over to that since it has the same noise reduction.
But on the latest version of Photolab I noticed that the editor part has become much better in speed and handling, so maybe it is worth to have.
I also have Topaz Denoise AI and while it is good, the latest Photolab is on another level.
--
Best regards
/Anders
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* Mirrorless, mirrorless on the wall, say which is the best camera of them all?
* Why don't I get a manual in Manual mode?
* Come to the Sony side, we have lenses...
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Some of my images:
https://www.dpreview.com/forums/post/65325637
https://www.dpreview.com/forums/post/64169208
https://www.dpreview.com/forums/post/64221482
https://www.dpreview.com/forums/post/65120847
https://www.dpreview.com/forums/post/65121520
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Article about how to FTP-transfer, edit & share RAW-images wireless out in the field:
https://www.dpreview.com/forums/thread/4609147
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Timeline over all mirrorless autofocus fullframe cameras:
https://www.dpreview.com/forums/post/65636058
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Article about Sony EVF/LCD modes:
https://www.dpreview.com/forums/post/65550258