1. An image processing method for performing dynamic range compression processing to a source image, comprising: a band image generation step for generating band images through extracting a portion of frequency components in the source image having a subject image falling thereon; a lowest-frequency image generation step for generating a lowest-frequency image having a lowest-frequency component extracted from the source image; a lowest-frequency image control step for performing conversion processing to the lowest-frequency image in accordance with a lowest-frequency function to generate a lowest-frequency controlled image; a controlled band image generation step for performing conversion processing to the band image in accordance with a high-frequency function, that is different from the lowest-frequency function, to generate a controlled band image; and an image processing step for performing dynamic range compression processing to the source image using the lowest-frequency controlled image and the controlled band image.