hi, i'm trying the official trial from autodesk
i saw that in any case a light is "renderable" on its backface even if you don't turn on the renderable checkbox and casts shadows from other lights
it was not like that on 2016 and wether more"fisically incorrect" it was ok
if you try to make a sphere light over a sphere object it will turn your object to black because of this behiavour
it will too block light from other lights in both directions

does somebody have the same issue?