1. An image acquisition apparatus for use with a microscope comprising: an image pickup element that acquires images obtained using the microscope; a change detector that detects the amount of change between an image acquired by the image pickup element and a subsequent image acquired by the image pickup element; and a binning means that performs binning processing by calculating and outputting cumulative pixel information of multiple proximate pixels of an input image as an output pixel so as to form a reduced-data output image, or that outputs pixel information of an input image as output data without reduced-data processing, based on the amount of change detected by the change detector; wherein reduced-data images as well as images that have not been reduced are output from the image acquisition apparatus.