The problem is indeed with the deferred shading. Here is an example of DX11 with Forward Shading (the default shading method) and with Deferred Shading:
It basically looks broken to me.
Deferred Shading is forcibly used when running in DX11 for all movable lights. Because my game has a day/night cycle, I’m using a DominantDirectionalLightMovable as my main light source, so all materials lit by it use Deferred Shading.
The only way I can see to prevent it being used, based on the documentation (UDK | DeferredShadingDX11), is to set all my materials to have EnableSubsurfaceScattering=True.
Materials that use Subsurface Scattering are ignored and the default Forward Shading is used (even if you plug nothing into the Subsurface Scattering inputs in the material).
Here is another example of the difference between Forward and Deferred Shading:
As you can see, the default forward shading looks far more detailed.
Does anyone know how to either fix Deferred Shading (so that it looks as good as Forward Shading), or how to disable it on an individual light (so I don’t have to change all of my materials to use Subsurface Scattering)?