[davidmanze]

   Maybe this image will shed some light (or lack of it) on the subject of noise in under-exposed subjects;

 

  I shot this forgetting to expose correctly.....the image is under-exposed by "4 full stops", as you can see there is very little to see if anything in the original exposure........bringing up the exposure to a normal level, low and behold there's plenty of image detail to be found!

 

  The image had a decent amount of noise reduction added, but what is left is usable considering the mess of the exposure I made.

 

                  What I like is the ISO invariance of the Nikon files, there is very little difference between a 4 stop underexposure at say ISO100 and a correct one at ISO 1600, when correcting for equal brightness in PP!

 

  Shot on the D500 at 250 ISO