Colorfulness is a non-technical term for the measure of how intense a specific color appears. Similar, but technically correct terms, are saturation and chroma (Munsell). Colorfulness can simply be said to be the degree of difference between a color and gray. But what gray? Saturation on the other hand takes into account that all colors are not equally bright when fully saturated: A blue is darker than a yellow for example. This means saturation is the colorfulness of a color relative to its own brightness. In general, terms such as saturation, chroma and colorfulness are used as synonyms. The more colorful a color is, the more vivid and intense it seems, while less colorful colors appear muted and closer to gray. When all color has been removed and saturation is 0, the image is called a gray scale image. There is an overlap between lightness and saturation in that a more saturated color appears lighter.
Lightness, or what is termed "value" in the Munsell color space, is defined as a given colors placement on a scale ranging from black to white. In the Munsell color space this scale is divided into ten equidistant steps. The term "lightness", on the other hand, stems from the HSL (Hue, Saturation, Lightness) and Lab color spaces. The term "value" is also used in the HSV (Hue, Saturation, Value) color space, but used differently than in Munsell. Value in HSV does not range from black to white, but from black to the fully saturated color. Paints can be made lighter or darker by adding white or black, but that also reduces saturation. "Tone" is an obsolete term that stems from darkroom photography to denote the lightness of a specific area of the print. Yet "tone" is still used in art where light and dark "tones" are built up with charcoal or similar drawing medium.
When working with digital images, you can simply calculate lightness as (r+g+b+)/3. That, however, does not take into consideration that green is the brightest color and blue the darkest. The relative brightness of the color channels is taken into consideration in the IUV color space, that calculates lightness like this: i=(76*r+150*g+29*b)/256. The formula reflects the fact that green is about twice as bright as red and red about 2 times brighter than blue.
In painting the term "tone" denotes an intermediate between gray and pure color. A mixture of pure color and white is called a "tint" while a mixture of pure color and black is called a "shade". In reality tint and tone are not as simple a it sounds, because though they do not have color in themselves, when white or black are mixed with a color, the color changes hue. In other words, black in mixtures behaves like a blueish color. For example if you mix yellow and black you don't just get a darker yellow, but you get a darker and greenish yellow. Similarly will an addition of white make a color appear colder.
In software you can digitally create tints and shades by converting from the RGB color space to IUV or Lab color space and alter the L (lightness) channel as described above. This will not alter the hue of the color as when you mix pigments with black or white.
Lightness, or what is termed "value" in the Munsell color space, is defined as a given colors placement on a scale ranging from black to white. In the Munsell color space this scale is divided into ten equidistant steps. The term "lightness", on the other hand, stems from the HSL (Hue, Saturation, Lightness) and Lab color spaces. The term "value" is also used in the HSV (Hue, Saturation, Value) color space, but used differently than in Munsell. Value in HSV does not range from black to white, but from black to the fully saturated color. Paints can be made lighter or darker by adding white or black, but that also reduces saturation. "Tone" is an obsolete term that stems from darkroom photography to denote the lightness of a specific area of the print. Yet "tone" is still used in art where light and dark "tones" are built up with charcoal or similar drawing medium.
When working with digital images, you can simply calculate lightness as (r+g+b+)/3. That, however, does not take into consideration that green is the brightest color and blue the darkest. The relative brightness of the color channels is taken into consideration in the IUV color space, that calculates lightness like this: i=(76*r+150*g+29*b)/256. The formula reflects the fact that green is about twice as bright as red and red about 2 times brighter than blue.
In painting the term "tone" denotes an intermediate between gray and pure color. A mixture of pure color and white is called a "tint" while a mixture of pure color and black is called a "shade". In reality tint and tone are not as simple a it sounds, because though they do not have color in themselves, when white or black are mixed with a color, the color changes hue. In other words, black in mixtures behaves like a blueish color. For example if you mix yellow and black you don't just get a darker yellow, but you get a darker and greenish yellow. Similarly will an addition of white make a color appear colder.
In software you can digitally create tints and shades by converting from the RGB color space to IUV or Lab color space and alter the L (lightness) channel as described above. This will not alter the hue of the color as when you mix pigments with black or white.