Extending CIELAB: Vividness, , depth, , and clarity,

TLDR

CIELAB is a widely used color space where a* and b* coordinates are often converted to chroma and hue, yet real‑world color changes involve simultaneous shifts in chroma and lightness under mixing or lighting. The study introduces two new CIELAB coordinates, vividness and depth, to better capture color perception. Vividness and depth are Euclidean distances from a color to L*=0 and L*=100, respectively, while clarity is the distance to the background color, and image visualizations illustrate how these variables affect perceived color. When color and background share the same lightness, decreasing chroma reduces color distinctness. © 2013 Wiley Periodicals, Inc., Color Research & Application 39:322–330, 2014.

Abstract

Abstract CIE L * , a * , b * is a rectangular coordinate system used extensively for numerical color communication and quality assurance. Often the a*, b* coordinates are rotated to cylindrical polar coordinates of (radial distance) and h ab (angle measured counterclockwise from the a* axis), reasonably relating to chroma and hue. When each coordinate is considered independently, it is observed that colors in our daily experiences do not change in a similar independent fashion. Changes in concentration for mixtures of colorants result in changes in both chroma and lightness. Directly illuminated three‐dimensional colored objects change in both chroma and lightness between direct illumination and either shadow or highlight. Two new coordinates are defined for CIELAB: vividness, , and depth, . Each represents a Euclidean distance from a color defined by L* and to of 0 and either L* = 0 for vividness or L* = 100 for depth. Image‐based visualizations were made to demonstrate how changes in these variables led to color changes more representative of our daily experiences. For cases where a color and background had the same lightness, it was observed that colors became less distinct with a reduction in chroma. A third dimension was defined, clarity, , a Euclidean distance from a color defined by L*, a *, and b * to its background color, similarly defined. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 322–330, 2014