A luminaire can comprise a system that automatically adjusts light output from the luminaire to control light level in an illuminated area. The system can increase light output if the light level in the area falls below a target light level or decrease light output if the light level in the area rises above the target. For example, when the area is illuminated by a combination of sunlight and luminaire light, the light level can be maintained at the target level by gradually decreasing light output as the sunlight contribution increases in the morning and by gradually increasing light output as the sunlight contribution decreases in the evening. The system adjustments can take into consideration whether the light level is offset from the target due to a change in the target or a short-term fluctuation that may be due to a cloud temporarily blocking the sun.