[davidmanze]

Tony Northrup posted a video on read noise with figures coming the site below:

http://www.photonstophotos.net/Charts/RN_ADU.htm

    Newer sensors such as the D850 and the D500 have a dual mapping system, which controls noise ......   this causes an increase in image noise until around 400 ISO, then the second mapping kicks in with less noise at 500 ISO than say 300 ISO.
   Cameras like the D800 and the D750 do not have dual mapping and their noise is directly related to ISO
 
    Nothing world shattering but it's worth a glance at the site to see where your camera lies ........
   the D500 for example has less noise at 400 ISO (second mapping) then at 250 ISO (first mapping).... given that is the area I am shooting, it's useful to know.

[wim]

BTW, the new (coming) Canon sensors will have a new type of system, where they actually will make use of a double set of sites somehow.

They're supposed to start using these by the end of this year, but it may well be into 2020 before we will really see those implemented in cameras.

Kind regards, Wim