A daylight harvesting light fixture has a housing defining a light aperture, a light emitting diode (LED) in the housing for providing illumination through the aperture, a power supply for supplying drive current to the LED; a photosensor for sensing ambient illumination through the housing aperture, and a control circuit programmed and connected for a) turning off current to the LED for a dark interval imperceptible to the human eye; b) deriving an ambient illumination level signal based on the photosensor output while the LED is turned off; c) calculating an LED light output complementary to measured ambient illumination to achieve a target ambient illumination; and d) restoring drive current to the LED at a level adjusted to produce the calculated complementary LED light output. This sequence may be repeated periodically to maintain a target ambient illumination.