Which color differencing equation should be used?

Color differencing equations have been used for quite some time. In 1976 the CIE published the first internationally endorsed color differencing equation. This formula called ΔEab or ΔE76 deemed a difference or ΔE of 1.0 to be the smallest difference perceivable by the human eye. This formula has been used in many ISO procedures such as 12647-2 for process control in the production of halftone color separations, proof and production prints. This color differencing equation made it possible to better communicate color differences under standard illuminants and observers. The color notation used for this equation was the L* a* b*-color space. It was soon discovered that this equation had its shortcomings. These shortcomings were, that it was not taken into consideration that the human eye is more sensitive to small colour differences in some regions of the color wheel and less sensitive in others. This means that a ΔE of 1.0 could be a small visible difference in one area of the visible spectrum (ie dark blue colors) and a large visible difference in another area (ie light pastel type colors).