An imaging system includes a first illuminator that irradiates a subject with light whose intensity varies over time; and a first imaging device that includes a first imaging cell having a variable sensitivity, and a first sensitivity control line electrically connected to the first imaging cell. The first imaging cell includes a photoelectron conversion area that receives light from the subject to generate a signal charge, and a signal detection circuit that detects the signal charge. During an exposure period, the first sensitivity control line supplies to the first imaging cell a first sensitivity control signal having a waveform expressed by a first function that takes only positive values by adding a first constant to one basis from among bases of a system of functions constituting an orthogonal system.