An image signal processing system according to the present invention has a function to perform image quality control in photographing a subject having a large difference in brightness in the surrounding environment so that the entire photographed image, in particular a subject which a user desires to view, has an adequate brightness and an adequate gradation. Specifically, this image signal processing system comprises: a video input unit, a video signal processing unit for performing signal processing on a signal output from the video input unit, and generating a video signal; an input-output characteristic control unit for controlling a characteristic of the video signal which the video signal processing unit generates; and a subject recognition unit for performing image processing on the video signal which the video signal processing unit generates, and recognizing and detecting subject information.