1. An image input apparatus comprising: an image pickup region including a plurality of pixels each for converting an optical image from an object into electrical image information and accumulating the electrical image information; and a processing circuit adapted to process the image information from said image pickup region, wherein said processing circuit generates image data by performing a subtraction operation and an addition operation on the basis of a plurality of first image information read out in a time-series manner from the same pixel during one exposure operation, and a plurality of second image information sequentially read out from the same pixel in a shielded state.