cameraExposure affects mip_cameramapIMAGE
Unfortunately an exposureNode always affects the image in mip_cameramap node - which is kind of stupid, because if one needs to tweak the light and colors of a rendering to match a backgroud image, there is no "true color" reference possible with mip_camera map.
don´t get me wrong, I compose in multiple layers and bring the original backplate back in later on in aftereffects. this question is just about tweaking the scene with reliable visual reference.
if someone knows a way to bypass the lensShader somehow for the mip_cameramap node it would be a great help.
everything starts and ends in the right place at the right time.