No, HDRMerge produces a RAW DNG file, which is still in the camera colorspace and encoded with a Bayer pattern. It is up to the RAW processing software (PhF in this case) to apply the appropriate demosaicing and color conversion.
In this case I did not use any intermediate scene-referred TIFF, I simply opened the HDRMerge output and saved linear Rec.2020 TIFFs at different exposure compensation values.
The HDRMerge output is a RAW image that is exposed like the darkest frame in the sequence (CRW_3012.DNG in this case), but with better details in the shadows that are taken from the brighter exposures.
I saved the following exposure steps from the HDRMerge output: -1, 0, +1, +2, +3.
Applying the same exposure compensation to CRW_3012.DNG would have provided similar results, but with much higher noise in the shadows:
CRW_3012.DNG +3EV:
HDRMerge output +3EV:
Enfuse applies a multi-level blending of the different exposures in order to achieve a compression of the dynamic range while preserving the local contrast.
To understand the difference, let’s compare the enfuse output with the result of a simple RGB curve that approximately gives similar brightness in the shadows and highligts.
enfuse output:
RGB curve applied to the scene-referred HDRMerge output:
As you notice, the second image is much flatter… in fact, there is no simple curve that can reproduce the enfuse output, because of the enhanced local contrast provided by the latter…