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Extending CIELAB: Vividness, V ab * , depth, D ab * , and clarity, T ab *
Author(s) -
Berns Roy S.
Publication year - 2014
Publication title -
color research and application
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.393
H-Index - 62
eISSN - 1520-6378
pISSN - 0361-2317
DOI - 10.1002/col.21833
Subject(s) - lightness , hue , mathematics , dimension (graph theory) , artificial intelligence , shadow (psychology) , optics , computer vision , euclidean distance , spectral color , euclidean geometry , color space , geometry , computer science , psychology , color model , physics , image (mathematics) , combinatorics , psychotherapist
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 ofC ab *(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,V ab * , and depth,D ab * . Each represents a Euclidean distance from a color defined by L* andC ab *toC ab *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,T ab * , 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