There is provided an image dynamic range compression system which can compress a dynamic range for which the visibility of a low-frequency image is ensured while preserving a high-frequency image. An image converting unit converts an input image into a compressed image having a narrower dynamic range than the input image. A high-frequency image extracting unit extracts a high-frequency image from the input image. An image synthesizing unit synthesizes a compressed image and the high-frequency image. Further, by adaptively changing synthesizing method of ensuring the visibility of images to synthesize, the image synthesizing unit synthesizes these images.