WM level from the nominal level that DOF sets so that the
   <i>apparent</i> brightness level of an attached LED varies linearly
   with the DOF level.  The eye perceives brightness logarithmically,
   so "half power" isn't the same as "half brightness".  Gamma correction
   compensates for this by remapping the DOF levels onto a logarithmic
   curve that better approximates the way the eye perceives brightness.
   This makes fades look smoother and makes brightness effects look
   more like what the game d