The Judd-modified chromaticity coordinates are related to the Judd-Vos-modified XYZ CMFs (Vos, 1978) by
where , , and are the chromaticity coordinates, and , and are the CMFs.
For more details refer to the Judd-Vos-modified 2 deg XYZ CMFs page.
Judd, D. B. (1951). Report of U.S. Secretariat Committee on Colorimetry and Artificial Daylight. In Proceedings of the Twelfth Session of the CIE, Stockholm (vol. 1, pp. 11). Paris: Bureau Central de la CIE.
Vos, J. J. (1978). Colorimetric and photometric properties of a 2-deg fundamental observer. Color Research and Application, 3, 125-128.