The recent upgrades to Qimage Ultimate where noise reduction has been improved and the related data is shown in the raw refine screen prompted me to do a little test. Here are the results:
I took some photos of some items in a dark corner in my office at the highest ISO available on my camera, 12800.
I used this very high iso to exaggerate the effects and make it visible on the small attached images.
The first exposure was with zero exposure compensation, the second with plus 1-1/3rd stops increase to move the camera histogram to the right.
See attached images below.
"Under exposed", QU pushed 12800 iso to 43460 with 10/10 noise reduction for Grain & Chroma
"Increased Exposure", QU pushed 12800 iso to 17940, with 10/10 Grain and Chroma noise reduction.

You can see the difference that "increased" exposure makes to the noise results in the processed image; one is poor, the other useable. I hope this is helpful to some of you, to improve technique to get the best quality from your camera and QU.  
Terry
PS. I obtained the camera histogram from the jpeg extracted from the raw. The raw histogram is, of course, modified by QU

Going back to my original post:
Here is the QU histogram for the underexposed image attached.
It's easy to see where the "ISO push" has occurred when compared to the camera histogram (also shown again).
Terry

QU has a histogram in it? 

Maybe a Printogram?

Mack

always good to read this sort of stuff as a reminder.

Indeed and what interested me were the images of the rabbit and the black cat at what he called the Optimum setting. See those in a viewfinder and you'd regard the as unrecoverable - or I would have done anyway.

Just been through last night's shots albeit quickly. It is interesting how many of the 12000 plus ASA ones are quite useable when you chuck enough exposure at them. Doubling the ASA so one can double the shutter speed seems to increase the keepers.

Tony