I'm not quite sure if it's possible to fix that, but if I use HardcoreDarkness with Brothers Johnson Unshaders, minimum sky lighting resets to default. Minimum block lighting is still dark.

I wouldn't mind removing parts of the shader pack if necessary, I just don't know which part affects the mod.

Shaders in general do not work with Hardcore Darkness because the rendering changes they do.

Thanks, I'll see what happens if I remove the shader-part from the ressource-pack.

For anyone who has the same "problem":
Inside the ressource pack, there's a folder assets\minecraft\mcpatcher\lightmap, if this is removed, HardcoreDarkness works as it should.

Oh i thought you were talking about actual shaders^^. Yeah for resource packs you have to remove the custom lightmap.