Rendering and Illumination - Autodesk AutoCAD 2013 Practical 3D Drafting and Design - page 341

• Mid tones : This adjusts mid-tones, that is, brightening or darkening inter-
mediate colors without modifying most bright or dark colors. It accepts a
value from 0 to 20 ; default is 1 .
• Exterior Daylight : This controls whether exterior daylight is considered
in the exposure or not.
• Process Background : This controls whether the applied background is
considered in the sure or not.