Colorfulness is the "attribute of a visual perception according to which the perceived color of an area appears to be more or less chromatic". A note accompanying this definition in effect implies that the perception of colorfulness evoked by an object depends not only on its spectral reflectance but also on the strength of the illumination, and increases with the latter unless the brightness is very high.
Chroma is the "colorfulness of an area judged as a proportion of the brightness of a similarly illuminated area that appears white or highly transmitting". A note accompanying this definition in effect implies that an object with a given spectral reflectance exhibits approximately constant chroma for all levels of illumination, unless the brightness is very high. Thus if a uniformly colored object is unevenly lit, it will generally exhibit greater colorfulness where it is most strongly lit, but will be perceived to have the same chroma over its entire surface. While colorfulness is an attribute of the color of the light reflected from different parts of the object, chroma is an attribute of the color seen as belonging to the object itself (called an object color ),and describes how different from a grey of the same lightness such an object color appears to be.
Saturation is the "colorfulness of an area judged in proportion to its brightness", which in effect is the perceived freedom from whitishness of the light coming from the area. A note accompanying this definition in effect indicates that an object with a given spectral reflectance exhibits approximately constant saturation for all levels of illumination, unless the brightness is very high.
