Something was not behaving as expected, so i did a simple ‘white furnace test’
Fully white diffuse sphere in fully white environment. Setting the specular to anything above one results in a an image where the sphere is brighter than the background!
That should never happen, right?
Eevee is the same… so i guess it is either a flaw in the pbr definition or meant to be like that?
Setting a mix between a diffuse and a glossy does not lead to that result (but specular to zero and metallic only in principled is also fine…)
here on blenderartists there is the thread with even more questions from other users:
e.g. setting the roughness on a fully diffuse shader leads to darkening and brightening in cycles. (Not so in Arnold)
here the screenshot: