Why objects reflected in the mirror are darker than original, as they were not receiving light The curtains are dark in the mirror image, as they were the original object but not receiving the light of a point lamp that i used nodes to define color and strength (blackbody and ies texture). The mirror shader i got from one answer here to &quot;realistic mirror&quot;, but the result is the same when I use a simple glossy bdsf, GGX (or others), white (RGB=0.8,0.8,0.8), roughness=0.000.
The other problem is that the translucent light that comes from  the window is different too...using &quot;realistic mirror&quot; it is brighter, and the simple glossy it becomes green! (I'm using cycles, an HDRI map for world and a point lamp)
You seem to have a (diffuse?)BSDF shader plugged into a glossy shader, this is not allowed by blender. Instead, add a mix shader, plug them both into it, and then plug the output into the material output.
This is just an example: