Characterizing the Accuracy of the Current CIE-standard and Cone-fundamental-based Spectral Luminous Efficiency Functions based on Achromatic Brightness Matches

The predictive accuracy of the CIE 2015 cone-fundamental-based spectral luminous efficiency functions (V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F2</inf>(λ) and V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F10</inf>(λ)) and the CIE 1924 2° V(λ) and 1964 10° V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</inf>(λ) functions were evaluated based on visual data from 54 observers in a 10° brightness and color (achromatic) matching experiment using eight different LED primaries. The CIE 2015 10° V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F10</inf>(λ) and 1964 V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</inf>(λ) functions outperformed the CIE 2° V(λ) functions, particularly in the cyan region. However, for primaries at 520 nm and 404 nm, the 2° V(λ) functions provided slightly more accurate luminance predictions than the 10° functions. The 673 nm deep red primary resulted in greater variability in matching brightness. Older observers exhibited similar trends to younger observers but with larger variations in brightness matching.