Wrong alpha values??


I have experienced something strange, maybe someone can help me with that:

So I have built a simple x-ray shader, put it on suzannes head. it renders just fine. But when I export it as a png with alpha and reimport it into the compositor of a new blender instance, the alpha values are different to the original (also the color, but that may be related to the alpha). Color management settings are the same in both blender files btw.

here is the rendered image with an alpha-over node:

I deactivate the alpha over node for export, and save it as 16 bit png with alpha:

reimported png in a new blender instance. clearly NOT the same image as before: