I'm doing research on daylighting facade systems and I encountered the following problem.
There are curved lamellas fitted just outside the window with reflective coating on top (plastic white 0,8 spec 0,8 roughness 0,015)
The reflective planes that are facing away from the camera (the lamellas above the camera) seem to ignore their specular setting. See image below:
Both renders are in 'maximum' quality and have exactly the same setup and settings. The only difference is the point of view is raised in the right picture.
Looking at the top of the desk, you see that both renders show significant difference in luminance!