Light and Darkness. This isn't perfect, but the rules provide no real feedback on how darkness penalties work other than a few vague references, so here is what I am going with until I come up with something better. There are more realistic solutions out there on the web, but the complexity is overwhelming.
Darkness modifier Situation
0 Outdoors during the day; multiple evenly spaced maximum continual light spells
0 Overcast day
0 Dim indoor lighting (torch-lit or lamp-lit building interior)
0 Well-lighted outdoor areas (multiple evenly spaced large bonfires)
-1 Dim-outdoor lighting (multiple evenly spaced small camp fires)
-2 Full moon
-3 Half moon
-4 Crescent moon
-5 Starlight (no moon); unlit building interior with windows at night
-6 Overcast night
-7 Total darkness; underground; unlit building interior with no windows at night (note: night vision ceases to function in total darkness; only dark vision functions at this lighting level)
Light Sources
Candle +2
Torch +7
Firelight +4 + (3*size in hexes)
Snow +6 (does not help in total darkness)
all light sources decrease in effectiveness by 1 for every yard distance starting 3 yards out. The penalty can never exceed the base lighting level regardless of distance.
example: Underground with a torch. -7, torch adjusts by 7.
Darkness penalty is 0 2 or less hexes away
-1 when 3 hexes away
-2 when 4 hexes away
-3 when 5 hexes away
-4 when 6 hexes away
-5 when 7 hexes away
-6 when 8 or more hexes away
after that the darkness is -7 (total darkness)
These penalties are based on the distance to the light source, so while you might be 40 yards away in total darkness, if your target is holding a torch, the darkness penalty is still 0.
Darkness modifier Situation
0 Outdoors during the day; multiple evenly spaced maximum continual light spells
0 Overcast day
0 Dim indoor lighting (torch-lit or lamp-lit building interior)
0 Well-lighted outdoor areas (multiple evenly spaced large bonfires)
-1 Dim-outdoor lighting (multiple evenly spaced small camp fires)
-2 Full moon
-3 Half moon
-4 Crescent moon
-5 Starlight (no moon); unlit building interior with windows at night
-6 Overcast night
-7 Total darkness; underground; unlit building interior with no windows at night (note: night vision ceases to function in total darkness; only dark vision functions at this lighting level)
Light Sources
Candle +2
Torch +7
Firelight +4 + (3*size in hexes)
Snow +6 (does not help in total darkness)
all light sources decrease in effectiveness by 1 for every yard distance starting 3 yards out. The penalty can never exceed the base lighting level regardless of distance.
example: Underground with a torch. -7, torch adjusts by 7.
Darkness penalty is 0 2 or less hexes away
-1 when 3 hexes away
-2 when 4 hexes away
-3 when 5 hexes away
-4 when 6 hexes away
-5 when 7 hexes away
-6 when 8 or more hexes away
after that the darkness is -7 (total darkness)
These penalties are based on the distance to the light source, so while you might be 40 yards away in total darkness, if your target is holding a torch, the darkness penalty is still 0.