fwiw… I was motivated to do this single raw shot pseudo exposure blending exploration because I was frustrated with the fact CNX2 and ACR would lose their willingness to recover highlight detail as the exposure slider was moved to the right. I could only reduce the blown out highlights within a given exposure slider value. Even though the detail in the highlights was in the RAW (NEF) file, these 2 RAW converters were not giving me that option and at the same time allow me to increase the overall exposure.
I have experienced the same, and (speaking only for ACR/LR here, I don't use Capture One) the best answer is to avoid
fighting the Recovery slider with the Exposure slider. There are occasions where one may wish to do this for specific local-contrast-tweaking reasons, but in that case the Tone Curve is more precisely controllable and more benign IMO.
Stepping back for a moment: when photographing a very large range of subject brightness, one protects the highlights by means of a
general underexposure (in absolute terms, as compared with the shutter/aperture one would have used if those same highlights had not been inside the frame). So the picture is in need of general lightening, except for the highlights (which we do not want to lighten).
Given the above, we are IMO better advised to use Recovery with the Brightness slider, instead of with Exposure.
Moving Exposure upward does lighten large parts of the picture, but it does so by shifting the whole upper part of the histogram
including the whitepoint to the right - and therefore moving the brightest pixels, toward clipping.
That's exactly what we want to do when we have an empty histogram at the right side (when we have not exposed "to the right"). But in other cases where there is valuable nearly-clipped data in the file, it's not what we want - and Recovery can only resist that tendency to a very limited degree. Also you very quickly start to lose hue accuracy and to introduce strange artefacts when using Recovery at very high values. So I sometimes even
reduce Exposure a little, even in an otherwise underexposed capture, so as to leave Recovery less to do.
Brightness tends to leave the whitepoint alone (assuming this has been placed at or near the right end of the histogram), and mainly lifts midtones - exactly what we require for the case in question (a fully-used histogram). Then we can tweak with Tone Curve afterward.
In summary, my own approach is: starting from the as-shot Exposure, look at the whitepoint (generally but not quite always, so as to fill the width of the histogram). Then see what detail is to be further gained in the highlights with Recovery; see what Brightness can do for the upper midtones and midtones (without worrying yet about the shadows), see what Fill Light can do for the shadow areas, see (gently) what Blacks can do to control contrast between the darks. Then tweak the Tone Curve (I like "points" mode for this) - to suit the subtler aspects of the picture.
regards, RP
I have been playing with HE, (Oloneo HDRengine) ... and have managed to tweek similer results ... although maintaing color fidelity is challenging!