A camera system, image processing method and computer program stored on a computer readable medium for image processing. Long and short accumulation images with longer and shorter exposure times are respectively obtained from one field. First and second long accumulation evaluation values are computed from the long accumulation image. A short accumulation evaluation value is computed from the short accumulation image. A short accumulation target exposure time and short accumulation exposure control information are acquired from the short accumulation evaluation value and a first target level. A long accumulation evaluation value is acquired by synthesizing the first and second long accumulation evaluation values. Long accumulation exposure control information is acquired from the long accumulation evaluation value and a second target level. An image is generated from the long accumulation image and the short accumulation image.