Command entry: 
Material Editor 
Standard materialBasic Parameters rollout for the Anisotropic, Multi-Layer, or Oren-Nayar-Blinn shader Diffuse Level group (unlabeled) or Advanced Diffuse group
Diffuse Level controls the brightness of the material's diffuse component.
Adjusting diffuse level
The material grows lighter or darker. Lowering the Diffuse Level dims the material's diffuse color without affecting the specular highlight. Diffuse Level is intended primarily so you can create a Diffuse Level map that makes portions of the material very dark.
Increasing this value increases diffuse brightness, and decreasing it reduces diffuse brightness without affecting the specular highlight. You can increase the diffuse level over and above the diffuse color's Value (in its HSV description). This parameter can range from 0 to 400. Default=100.
Click the map button to assign a Diffuse Level map. This button is a shortcut: You can also assign a Diffuse Level map on the Maps rollout.
