Below are the key points:
2) Sony a7R III Nearly Matches Chart-Topping Nikon D850: At ISO 100, the a7R III dynamic range actually exceeds that of the D850, thanks to incredibly low read noise. That’s impressive for a camera constantly running its sensor in live view.
3) The Sony a7R III shows a 0.42 EV, or nearly a half a stop, improvement in base ISO dynamic range over the a7R II. That’s not insignificant: it will be visible in the deepest shadows of base ISO shots of high contrast scenes.
4) As for Sony’s marketing, it sounds like the claim of 15 EV is believable, but only technically if you consider how your images look when shrunk to 8MP files. To be fair, there’s some benefit to comparing dynamic range figures after resizing camera outputs to 8MP, since it’s a common basis for comparison that doesn’t penalize cameras for having higher resolution (and therefore smaller pixels).
Read the full review at DPReview.
See also: Nikon D850 vs Sony a7R III Specs Comparison.