Effects of Light Sources (DMG)

The types of lighting and their radii are given in the Player's Handbook. However, these represent only the most basic effects of a light source. There are other effects of carrying a light that do not lend themselves to easy quantification or simple tables.
==Being Seen==
If player characters are using light to find their way, then not only can they see, but they can also be seen. Hiding one's light is impossible in this case. Characters using a light to find their way can even be watched by creatures beyond the range of their own light. Since the light source illuminates the area around the player characters, it makes them visible to people or creatures out to the watchers' normal visibility ranges. The radius of the light source isn't the issue in this situation.
For example, on a clear plain, a raiding party of orcs could easily see the light of a fire and the silhouettes cast by the characters, even at 1,500 yards. Indeed, since the brightness of the fire is so different from the surrounding darkness, the light would be noticeable at even greater ranges, though details wouldn't be. Unless characters using a light source take special measures (posting a guard in the darkness, for example), they cannot surprise creatures who can see the light of their fire, torch, or lantern.
==Creatures and Light Sources==
Light sources, particularly fires, tend either to attract or chase away creatures. Wild animals tend to avoid lights and fires, especially if hunters frequent the area. On the other hand, animals that hunt player characters (or horse meat) will be attracted to a fire. They have learned that fires signal a source of food.
Intelligent creatures always approach a light source with caution. Friendly NPCs don't know if they are approaching the camp of a friend or foe. Hostile NPCs will likewise get as close as they can without revealing themselves, in order to learn the strength and numbers of the enemy. Only a few NPCs—those wishing to avoid all danger—flee at the sight of a fire, generally heading away from it in the opposite direction.