**System Information**
win 7 + gtx970
**Blender Version**
Broken: (example: 2,74 165598e 32bit + 64bit
**Short description of error**
In cycles
In complicated scenes with a large number of lights the darkness of the scene despite brightening light and make noise.
All Bug see in Hidden lamps cause noise and darkening the scene.
A big nuisance.
**Exact steps for others to r{F171398}
{F171399}eproduce the error**
You render my file LAMP+SUN-bug.blend with there are lights and no lights in Cube ( lamps in layer nr10 ) .