n Redness–greenness coordinate in certain transformed color spaces, generally used as the Δa, or difference in “a” between a specimen and a standard reference color. If “a” or Δa is plus, there is more redness than greenness; if “a” or Δa is minus, there is more greenness than redness. It is normally used with b or β as part of the chromaticity or chromaticity difference (McDonald R (1997) Colour physics for industry, 2nd edn. Society of Dyers and Colourists, West Yorkshire, England; Billmeyer FW, Saltzman M (1966) Principles of color technology. Wiley, New York). See Uniform Chromaticity Coordinates.
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Gooch, J.W. (2011). “a” or “α”. In: Gooch, J.W. (eds) Encyclopedic Dictionary of Polymers. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-6247-8_2
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