Light on this mud follows the following scale.  It is graduated and every race 
has the ability to see in some range of light.  If the light gets to dark or to 
bright, certain races will not be able to see.
 
Magically darkened room  <0
Absolutely dark room      0
Standard dark room        5
Dimly lit room            20
Mine shaft with candles   30
Partially lit room        50
Well lit room             60
Shaded forest             60
Brightly lit room         80
Direct Sunlight           100
Explosion or flash       >200
 
Human      20 - 200
Lizard Man 40 - 200
Elf         5 - 180
Half-Elf   20 - 190  
Dwarf       5 - 150  
Gnome       5 - 150
Half Orc   10 - 110
Duergar     0 - 130
Goblin      0 -  90
Drow       -5 -  90
Orc         5 -  90
Troll       0 -  80

The vision starts to fuzz out 5 levels above the bottom racial limit
and you are totally blind 5 below the lower end of the range.

At the top end things are slower, assuming that you can squint, shade your
eyes etc. You won't be TOTALLY blind till 40 points above the nominal maximum.
