1. An imaging apparatus comprising: an image capturer configured to generate a plurality of short-exposure images by performing continuous imaging for a first time in a first imaging mode in which imaging is performed through exposure over the first time; a processor configured to control the image capturer to generate at least one short-exposure image through performing additional imaging after the first time if an imaging command is input in a state where the first imaging mode and an HDR (High Dynamic Range) mode are set; and an image processor configured to synthesize the short-exposure images generated by the image capturer by successively accumulating the short-exposure images.