An object of the present invention is to provide an imaging system capable of improving S/N ratio and increasing dynamic range and a method of driving the imaging system suited to the improvement and increase. An imaging system includes: a solid-state imaging device having a plurality of pixels arranged in a matrix, column amplifiers each corresponding to each of columns of the pixels and an output portion for outputting an image signal based on an amplification by the column amplifier; and a signal processing portion receiving the image signal, wherein the column amplifier amplifies a signal output from the pixel by a gain q larger than 1, and the signal processing portion multiplies, by a factor less than 1, the image signal based on the signal amplified by the gain q.