I've been using Blender for a few years now and never given this much thought, but I just started learning more about different PBR workflows, and I'm realizing I don't understand the Specular input in the Principled BSDF.
In the past I've tended to adjust it to whatever looked the best for the specific material and scene, but that doesn't seem like a very accurate workflow, especially when using texture sets with multiple materials (eg. from Substance Painter).
Often I've left it at the default value of 0.5, but this seems to make certain materials too bright and plastic-looking, for example with some types of rubber.
For some projects I've also connected it to the inverse of the roughness input, but I can't imagine that's very accurate either.
So I'm wondering what IS the "correct" or most accurate method? Is there a specific value that it should always be set to, or should I be creating Specular maps to use with it?
And how would this translate to other software, like Maya or Houdini?