1. An image pickup device comprising at least: an image pickup section that picks up a long-time exposure image having a relatively long exposure time in unit period and a short-time exposure image having a relatively short exposure time in the unit period; a combining section that combines the long-time exposure image and the short-time exposure image, obtained by the image pickup section, with each other, to generate a combined image, the exposure images being combined with each other on the basis of a ratio between the exposure time of the long-time exposure image and the exposure time of the short-time exposure image; a dynamic range calculating section that calculates a dynamic range of an object for the combined image generated at the combining section from the long-time exposure image used in the combining operation, the exposure time of the long-time exposure image, the short-time exposure image used in the combining operation, and the exposure time of the short-time exposure image; a storage section that holds base compression curve data corresponding to a few types of dynamic ranges; and a compressing section that, using the base compression curve data held in the storage section, calculates a compression curve suitable for the dynamic range of the object calculated by the dynamic range calculating section, and that generates a compressed image in accordance with the calculated compression curve, the compressed image being generated by compressing the combined image generated by the combining section, wherein an image subjected to a gradation compression operation in accordance with the dynamic range of the object is generated from the long-time exposure image and the short-time exposure image obtained by the image pickup section.