Is posible with cycles create emision material with negative values? I look for solution on absorption light with object for darkening spots in scene.
Of course, it is possible… Just set a negative value for the Strength.
Beware of the color of the light! That’s the color that will be absorbed. For example, to make a scene fade to red ® in some area, you must use a cyan light (G+B).
I think I have an image using negative light. 2 secs…
The spots are modeled so that there is a rim of negative white light around the hole where the light comes from. It prevents the light from spreading all around.
Note that this isn’t the best possible example of the use of negative light. 
It was just an experiment.
Thanks.
This is wonderfull effect ^^
Color light, thats I make my mistake. My color was black so absorptions spectum was black also and negative valus not afecting brightness of scene.
https://www.youtube.com/watch?v=FVeDlqN6wQc on youtube is explanation 