Abstract
We previously found the effect of colorfulness-adaptation in natural images. It was observed to be stronger in natural images than unnatural images, suggesting the influence of naturalness on the adaptation. However, what characteristics of images and what levels of visual system were involved were not examined enough. This research investigates whether the effect of colorfulness-adaptation is associated with spatial frequency components in natural images. If adaptation was a mechanism in early cortical level, the effect would be strong for adaptation and test images sharing similar spatial frequency components. In the experiment, we examined how the colorfulness impression of a test image changed following adaptation images with different levels of saturation. We selected several types of natural image from a standard image database for test and adaptation images. We also processed them to make shuffled images with spatial frequency component differed from the originals and phase-scrambled images with the component similar to the originals, for both adaptation and test images. Observers evaluated whether a test image was colorful or faded. Results show that the colorfulness perception of the test images was influenced by the saturation of the adaptation images. The effect was the strongest for the combination of natural (original) adaptation and natural test images regardless of image types. The effect for the combination of phase-scrambled images was weaker than those of original images and stronger than those of shuffled images. They suggest that not only the spatial frequency components of an image but also the recognition of images would contribute to colorfulness-adaptation.