A physically meaningful base albedo is around 0.18–0.2, not 1.0, for correct lighting response

Beginners often set a ‘white’ material to RGB(1,1,1) and a ‘red’ material to (1,0,0). In physically motivated rendering the albedo of a mid-grey real-world material is around 0.18 (18% reflectance, the standard photographic grey card). Setting albedo to 1.0 makes the surface a perfect mirror reflector and causes unrealistic blown-out highlights. Using ~0.2 keeps values predictable: the key light can be set to a natural intensity and materials respond in a controllable way. This also prevents pure blacks (albedo 0) from being unlit and uncontrollable.

Examples

Grass albedo in reality: ~0.2. So in GLSL: vec3 mat = vec3(0.2, 0.2, 0.2); for a middle-grey, then multiply by the lighting equation.

Assessment

Why does setting albedo to 0.0 (pure black) make a surface impossible to adjust with any lighting or color-grading operation?