1. An imaging-observation apparatus comprising: an image capturing section configured to shoot a subject under multiple different shooting optical conditions at the same time and sequentially generate a plurality of images under those multiple different shooting optical conditions; a display control section configured to accept an operator's input; an image synthesizing section configured to synthesize together the plurality of images in accordance with the input to the display control section at a synthesis ratio specified by the input and to sequentially generate synthetic images one after another; and a display section configured to present the synthetic images.