Strange behaviour when adjusting offset

alx

I am using an ASI 120 MM-S and ASIcap (v2.5.6) with SDK driver v3.17.
When trying to change the offset (''brightness'') at constant commanded gain (30), I found the strange following results:

in MONO16 with any binning (or in MONO8/Binning=1), the true adu mean value are correctly equal to 16 times (resp. 1 time) the value of the offset and the sigma is consistent with your quoted readout noise of 4 e/adu.
in MONO8 and BINNING=2, the true adu mean value seems to rather obey the equation: ''-2 + 4*brightness''. In addition, the histogram looks like to be 4 times broader than in BINNING=1, while it should be 2 times narrower.
Of course, input signal was the same in each configuration (the obscurity actually).
Can you explain ?
Regards,
alx.

alx

Since there is no reply nor comment, I just simplify my question:
Everything seems to happen as if
- in MONO16, BIN=1 or 2, and MONO8 BIN=1 : the binning was an average
- in MONO8, BIN=2 : the binning was a sum.
Is ZWO agreeing with that ?

Tech@ZWO

alx https://astronomy-imaging-camera.com/tutorials/everything-you-need-to-know-about-astrophotography-pixel-binning-the-fundamentals.html
Here is an article for your reference(fifth).