Thanks for the reply. My info came from this blog: DONTNOD Physically based rendering chart for Unreal Engine 4 | Sébastien Lagarde
“…the base color (the one use by the non-metallic) must be in the range of the first gradient 50-243.”
I took that quote to mean that no texture should have an average value less than 50 RGB.
Since making the above post, I have completely reinstalled the engine and started a fresh map, which seems to have eliminated a lot of problems. That and I realized the default brightness for a directional light (10) is very high and overly brightens everything. I notice on some of Epic’s work they use 3.1415 (pi?). Is there a reason for this? Is this a physically accurate default value?
EDIT: Ok, apparently, using 16-bit PSDs was causing the engine to brighten the textures on import. Using good old TGAs solved that.