To acquire illuminance component data showing the effect of an illuminance environment on an image.

A digital camera 1 is provided with a movable diffusion plate 116 in front of a CCD 112. When a shutter button 122 is depressed half way, the diffusion plate 116 is placed on an optical path leading to the CCD 112. The diffusion plate 116 brings incident light to the CCD 112 into color mixed conversion light so as to acquire the color component data of the conversion light. Since the conversion light in a color mixed state has a spectral optical distribution more flat than that of a substantial spectral reflectance of an object, the spectral reflectance of the conversion light is regarded to be almost constant. Thus, the illuminance component data showing the effect of the illuminance environment on the image can be acquired.