The present invention is an apparatus, system, method, computer program, and computer program product for controlling window coverings to adjust admitted daylight. More particularly, the present disclosure plates to a control system for controlling the amount of daylight admitted through adjustable window coverings. In an embodiment of the present invention, the system includes a stand-alone open loop proportional control subsystem including a calculation or algorithm that is operable to convert a sunlight sensor signal to a blind slat position based on a predetermined curve stored in memory. In another embodiment of the present invention, the system is operable to transmit the sunlight sensor information, for example, such as in Lux, to an external system, which may then provide blind slat position requests based on some other curve, algorithm, or user need. The blind slat position may be controlled by the system to avert undesirable solar heat gains and also achieve significant daylight harvesting.