Event cameras are sensors that asynchronously measure the brightness change of each pixel with a microsecond-level time resolution. They have reduced motion blur and a dynamic response range of up to 140 dB, which allows them to handle extreme lighting conditions better than traditional frame cameras. Most of the research on event cameras has focused on dynamic vision, neglecting their potential applications in static scenes. This paper investigates how event cameras respond to stationary objects and provides a comprehensive theoretical analysis. We show that the event camera’s output depends on the brightness of the objects and their circuit structure. We also derive a mathematical formula that relates the event camera’s sensitivity to the number of absorbed photons. Furthermore, we propose a method to modulate the stationary output of event cameras.