I’d like to set the record straight. Doom’s lighting system goes by 16 units! Too many times I’ve seen levels going by 10 or even 8 units. Light levels between 16 intervals get rounded down. For instance, if you set a sector’s light level at 150, it becomes 144.
I recommend always using smoothed lighting in maps. This means all adjoining sectors have lighting either 16 above or below its neighbours. Lighting must have a specific source. For example, a florescent light in an alcove, a window, or a skylight. The lighting of a map should match the sky corresponding with it. The first eleven levels of Doom II should have been darker outside areas since the the sky represented what looks to be dawn.
When I asked John Romero why lighting is by 16 units, he responded, “I believe it was so Carmack could store the value in a nibble (4-bits, which is 0-15).” OK so that means nothing to most level designers.
Lighting effect sector types such as pulsing or flickers like fire need lighting differentiation of at least 32. These work well set at a high light level like 208, surrounded by a dim 128. Another good effect is two sequential sectors set 208, then 176, both with a sector lighting effect. Then set the surrounding sector with a 144 light level.
Light levels should be 255, 208, 192, 176, 160, 144, 128, 112, 96, and 0. 16 through 96 are the same considering limitations in the palette and colour map. 255 is full-bright meaning no matter what distance you are from the sector, the colour of the textures and flats are always the same. 255 is good for lighting sectors using a texture containing more rare Doom palette colours such as light blue or purple. Example: The Darkening E2 blue light textures. 192 and 176 are useful for outdoor areas but pay attention to what sky you’re using!
One fun lighting effect I created years ago is vertical lighting on walls. You create sectors 1 unit wide within a wall with 16+ light levels as the ceiling levels rise. You will see this effect in an upcoming Crucified Dreams map.
Figure: Vertical lighting
Dark lighting is useful for hiding enemies in shadow. Try placing enemies in dark sectors with light behind them to cause a silhouette appearance. Many new mappers make the mistake of going too bright or in the opposite direction, so dark you can’t see attacking enemies.
Lighting should enhance the beauty and atmosphere of a map, so use it! Here are some recommend WADs that display the usefulness of lighting.