Tuesday, June 17, 2008

Color Theory: Q & A Part 2 - Chroma

This is a continuation of the Color Theory: Q & A generated by my first Color Theory post. While I'm moving to California, I thought I'd post a series of these scheduled to appear every other day. Discuss amongst yourself until I return to the Wiemanomiconosphere.
Q: Aren't "chroma" and "saturation" the same thing?
A: Yes and no.
Chroma is the strength or intensity of a color. More specifically, it is the amount of departure of a color from a gray of the same value. Munsell believed that "saturation" was used to indicate a combination of value and chroma. From page 7 in the New Munsell Student Color Set:

Albert Munsell's way of thinking about saturation parallels the definition of saturation in chemistry -- when a liquid cannot absorb more of a substance, it has become saturated. The term "saturation" is often used by painters to indicated the relative proportion of pigment to filler, or medium, in a paint. When the term saturation is used with this meaning, a pure black is a saturated color. This is entirely different from what is meant by chroma. Black is a neutral color, it has no chroma. On the other hand, when used to mean the strength of a color, saturation becomes a synonym for chroma. In this case, a saturated color is one with strong chroma. Once again the way words referring to color are used in everyday conversation leads to confusion. Because of the misunderstandings caused by all the terms used to indicated the same attribute of color, Munsell chose to use the word "chroma."
The following picture is of the 7/ row of the Hue: 5YR color chart. All of these chips are the same hue, 5 YR (a.k.a. orange), and have the same value, 7/. The variation among these chips is chroma.From left to right the chips' chromas are /2, /4, /6, /8, /10, and /12. The color of the chip on the far left does not depart much from a gray of the same value, so it has weak or low chroma. The chip on the far right departs a lot from a gray of the same value, so it has strong or high chroma.

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