I was caving and noticed that the light levels did not change, the game kept rendering everything in light level 15, I'm pretty sure.

Using canvas 1.17-1.0.1578

Which pipeline do you have active? With dev the lighting is crazy wrong, which is why it is still dev...

I think it was dev, I'll try with the other pipelines later

With the basic pipeline

It should be almost pitch black

Interesting. Two more questions: 1) Any other mods present and 2) does it happen in any enclosed space (include new digs) or only in some areas? If it's specific to area, what's the Y-level and biome here?

The only mod I was using was canvas, and it does happen with enclosed areas. I don't think it's specific to the area.

When changing pipelines, especially from/to Dev or third-party, make sure to recompile (default Hotkey '=') or you might not see proper light levels. This is fixed in #262.

It's not canvas, it's my vanilla game. I don't know why it's not displaying light levels below 15.

I fixed the issue, I had to update the brightness setting.