Chapter four: perce iv i ng and recogniz i ng objects. half of the vision field is missing. Half relative to fovea, if it is the left visual field then left vision not working. one is in left visual field and the other eye has visual field defect in right visual field. In left eye, the left part is missing. In r ight eye the right part is missing. The brain structure is the optic casism, it is the part where visual information is crossing over. wat is csf-contrast sensitivity function. Humans limited to 60 cycles spatial frequency inverted u. On the vertical axis is contrast sensitivity function. Inverted u means ? middle (midlevel) vision loosely defined stage of visual processing that comes after basic features have been extracted from the image, early vision, and before objet recognition and scene understanding, high level vision.