An image pickup apparatus comprising: an image pickup device for picking up an image of a subject; a signal processing section for generating a composite image having a relatively wider dynamic range than at least either the dynamic ranges of a long-time exposure image picked up with a relatively long exposure time by said image pickup device or a short-time exposure image picked up with a relatively short exposure time by said image pickup device, the signal processing section comprising a synthesis section for generating the composite image from said long-time exposure image and said short-time exposure image on the basis of a switch luminance signal level determined from said image signals, said synthesis section operable to acquire, from said short-time exposure image, said pixels corresponding to at least a higher luminance signal level than said switch luminance signal level among pixels constructed in said composite image; and said synthesis section acquires, from said long-time exposure image, said pixels corresponding to at least a lower luminance signal level than said switch luminance signal level among said pixels constructed in said composite image, and a control section for dynamically varying the assignment proportion of a high luminance dynamic range to a low-middle luminance dynamic range in a dynamic range of an output image to be outputted as a video signal when generating said composite image, characterized in that a correction function that is dependent on the area of the high luminance region which occupies said composite image is used by the control section to determine variations to the relative proportions of the dynamic ranges so as to improve the greyscale reproducibility of the low-middle luminance region, and by further comprising a compression section for dynamic range compression of said pixels corresponding to at least a higher luminance signal level within the proportion of the dynamic range of the output image assigned to a high luminance dynamic range, and compressing said pixels corresponding to at least a lower luminance signal level within the proportion of the dynamic range of the output image assigned to a low luminance dynamic range in said generated composite image. an image pickup device for picking up an image of a subject; a signal processing section for generating a composite image having a relatively wider dynamic range than at least either the dynamic ranges of a long-time exposure image picked up with a relatively long exposure time by said image pickup device or a short-time exposure image picked up with a relatively short exposure time by said image pickup device, the signal processing section comprising a synthesis section for generating the composite image from said long-time exposure image and said short-time exposure image on the basis of a switch luminance signal level determined from said image signals, said synthesis section operable to acquire, from said short-time exposure image, said pixels corresponding to at least a higher luminance signal level than said switch luminance signal level among pixels constructed in said composite image; and said synthesis section acquires, from said long-time exposure image, said pixels corresponding to at least a lower luminance signal level than said switch luminance signal level among said pixels constructed in said composite image, and a control section for dynamically varying the assignment proportion of a high luminance dynamic range to a low-middle luminance dynamic range in a dynamic range of an output image to be outputted as a video signal when generating said composite image, characterized in that a correction function that is dependent on the area of the high luminance region which occupies said composite image is used by the control section to determine variations to the relative proportions of the dynamic ranges so as to improve the greyscale reproducibility of the low-middle luminance region, and by further comprising a compression section for dynamic range compression of said pixels corresponding to at least a higher luminance signal level within the proportion of the dynamic range of the output image assigned to a high luminance dynamic range, and compressing said pixels corresponding to at least a lower luminance signal level within the proportion of the dynamic range of the output image assigned to a low luminance dynamic range in said generated composite image.