I’d like to set the record straight. Doom’s lighting system goes by 16 units! Too many times I’ve seen levels that go by 10 or even 8 units. Light levels between 16 intervals are rounded down. For instance, if you set a sector’s light level at 150, it will be rounded down to 144.
I personally recommend always using smoothed lighting in maps. This means that all sectors meeting each other will have lighting either 16 above or below the neighboring sectors. All lighting should have a specific source. For example, a florescent light in an alcove, a window, or a skylight. The lighting of a level should match the sky which corresponds with it. The first eleven levels of Doom II should have all had darker outside areas since the the sky represented what looks to be dawn.
When I asked John Romero why Doom’s lighting is done by 16 units, he responded, “I believe it was so Carmack could store the value in a nibble (4-bits, which is 0-15).” Um yeah, that means nothing to level designers. 
Lighting effect sector types such as pulsing or flickers like fire must have lighting with a difference of at least 32 of a neighboring sector. These work nicely set at a high level of light, such as 208, set and the lighting surrounding is set at a lower level such as 128. Another good effect is having two similar sectors together, such as 208, then 176, both with a sector lighting effect then a 144 light level for the other part of the area without the lighting being changed.
Light levels used should be 255, 208, 192, 176, 160, 144, 128, 112, 96, and 0. Light levels from 16 to 96 are really the same light level considering the Doom’s limit colour palette. 255 is full-bright meaning no matter what distance you are from the sector, the colour of the textures and flats in it will always stay the same. 255 is a good light level to use in a lighting sector which has a texture in it which is more rare in the Doom palette such as light blue or purple. Example: The Darkening E2 blue light textures. 192 and 176 are usually useful for outdoor areas but pay attention to what sky you are using!
One fun lighting effect I created years ago is vertical lighting on walls. You create multiple sectors 1 unit wide within a wall with 16+ light levels as the ceiling level of each rise. You will see this effect in an upcoming map of Crucified Dreams.
Figure: Vertical lighting
Dark lighting is useful for hiding enemies behind the shadows or even try placing enemies in dark sectors with lighter sectors behind them giving off a silhouette appearance. Many new level designers make the mistake of creating levels which are either too bright or even so light that you can’t see any enemies attacking you.
Lighting should be used to enhance the beauty and atmosphere of a map, so use it! Here are some WADs I recommend displaying the usefulness of lighting.
