1.0 What It Actually Does
Isolates the raw diffuse color, completely stripping away lighting, shadows, and reflections.
The Problem: You think "Unlit" mode shows your BaseColor. It doesn't. Unlit is influenced by Metallic and Specular.
- The ramp by default is using the range of luminance [Charcoal 0.02 - White Paint 0.95]
- Debugging converts the baseColor values to the color space Unreal uses for luminance, Linear sRGB REC709
Albedo Debug reads BaseColor as calculated in the GPU, the different thing is DiffuseLum, it shows how Metallic physically darken your BaseColor. If you have a 0.05 BaseColor but high Metallic, DiffuseLum reveals the true, darker value rendered by the GPU in the final image.
The two Images below represent the Split Screen Mode, when checking BaseColor Only, it'll replace Lit by GBuffer BaseColor, when Split Screen is off, it replaces the whole debug mode with GBuffer BaseColor
Metallic Contribution Switch is for what's mentioned above, if you disable it, you'll debug BaseColor by itself without the influence of Metallic & Specular on it. As the example below, it gives you a warning that your metal might look dark in some places or lighting scenarios.
