There is another mention on Keith's page, supposedly from an actual tester of the 5dsR, that says: "Low ISO DR is put at 1.5-2 stops better than the 1D X, but high ISO performance (6400) falls marginally behind the 7Dmk2".
Hi Geraldo,
I take those comments as subjective, they are just impressions. But I put them in the same category of previous claims about the 16 stop DR of medium format Digital backs, not substantiated by cold hard facts.
Hummm... But if that is true, why Canon isn't using it as marketing?
Probably because Canon knows it isn't so. What may be true, but we'll have to wait and see, is that the pattern noise is reduced. That would be helpful, because the remaining read-noise + low shot-noise is more random (easier to remove) and less obnoxious. It allows better demosaicing as well, if one doesn't have to hold back in order to avoid amplifying pattern noise.
The way I read the comments so far, is that it is mostly due to the help of the dual Digic6 performance that the data can be cleaned up a bit, but that the inherent CMOS electronics have not been improved enough to really lower the read noise like on the Sony sensors. Which is already something if you account for the much smaller sensels.
So read noise is probably about the same, pattern noise is reduced, and
the photographic S/N ratio (not that of the sensor in isolation) is improved due to denser sampling of the lens projected image. There may be other improvements in lower noise generating components, but that would be unsubstantiated speculation. Let's wait for the DxO analysis on noise and DR (I expect 11.5 stops or slightly more), or for people to get their hands on some Raws to analyze.
I expect an overall cleaner image, with higher resolution, and more robust data for post-processing due to the improved photographic S/N ratio. Let's also not forget the role of the Raw converter. Some converters are consistently producing technically better, more easy to work with raw conversions, and others do all sort of funky tone compression stuff that first needs to be tamed, if the aliasing and mazing artifacts are even not creating another challenge. Capture One offers a very nice low artifact conversion, with lots of control that is not swamped with under the hood automatic tone adjustments (unless the user specifically tells it to have a go).
I recently had a look at Canon DPP's Digital Lens Optimization (DLO) for images I shot with the older EF 16-35mm f/2.8, and the DLO even improved the corners towards being useful. The DLO creates and embeds an additional corrected Raw instead of just postprocessing the Raw converted data, which kind of proves that Raw converters (working on better Raw data) and intimate knowledge/understanding of the Raw data can make a huge difference. Luckily Canon has (so far) not taken the route to actively reduce noise or compress tone-curves by default, before writing the Raw data. The data quality is usually as Raw as Raw can be (including an offset to not cripple the read noise), which offers an excellent starting point for those who know how to do a proper Raw conversion.
Cheers,
Bart