ANSI continues advancements
on SSL chromaticity standard
JIANZHONG JIAO describes the work of a new ad hoc group within ANSI that is contemplating how to
accommodate the perceptions and preferences of humans in terms of the chromaticity of white light
relative to the black-body locus.
standards | CHROMATICITY
The newly published 2015 version of the American National Standards Institute (ANSI) LED lighting chromaticity standard, ANIC C78.377-2015,
incorporates support for new LED lighting
products in the lower correlated color temperature (CCT) range — for example, 2500K
and 2200K. The new version also provides
guides for the LED makers and users with
higher color consistency with the recommended four-step MacAdam ellipse equivalent quadrangles and circles. But the ANSI
mission is based on continuous improvement. And a new ad hoc group has formed
at ANSI to work toward recognition of the
perceived or preferred white colors below or
above the black-body locus.
The ANSI chromaticity standard is a communication tool used between LED makers
and users, standardizing the white color
variation and tolerance for indoor lighting
applications. We covered the new standard
in detail in an article published in February
2015 ( http://bit.ly/1Eniyf E).
During the development of the ANSI
chromaticity standard, the experts took a
logical approach to determine the targeted
CCT center-points that form a white curve
by connecting the black-body locus in the
lower CCTs to the daylight of illuminant
D65. So far, in the 2015 version of the ANSI
chromaticity standard, the white curve
covers the CCT range from 2200K to 6500K.
The tolerance from the white curve, or the
color consistency, is specified using the
nominal CCTs, fixed or flexible, with the
deviations. The deviations are described
by either the seven-step or four-step Mac-
Adam ellipse equivalent quadrangles or cir-
cles. By using these quadrangles or circles,
LED makers can further determine the LED
binning methods or themes that may effi-
ciently use the yields of the LED products;
therefore, this standard is also widely used
for LED makers to establish the LED col-
What is white?
The quadrangle tolerances form a continuous white region from 2200K to 6500K on the
chromaticity diagram, making the LED binning specification relatively easier. Within
the region, the binning grids can be formed
DR. JIANZHONG JIAO is an independent consultant for LEDs and lighting technologies. He
is an internationally recognized lighting expert. He has been actively involved in LED and
LED lighting standard development activities, technical conferences, and industry consortia.
He serves as the past chair of the SAE Lighting Committee, past chair of NGLIA, and past
chair of the NEMA SSL Technical Committee. In IESNA he serves as the treasurer of the
Testing Procedures Committee, member of the Roadway Lighting Committee, vice chair of the
Computer Committee, and vice chair of the Light Source Committee. He is the vice chair of
the ANSI SSL Light Source Working Groups, chair of the ASABE Electromagnet Radiation for
Plants Committee, a member of the Standard Technical Panel of UL8750, and
a member of the standard committees in IEEE, CIE-USA, SEMI, and JEDEC.
He is the organizer and chair for SAE World Congress Lighting Technology
Conference, a member of the Organizing Committee and chair of SPIE SSL
Symposium, and a member of the Technical Panel of Strategies in Light. He
can be reached at j_ firstname.lastname@example.org.
FIG. 1. At LRC, scientists conducted color rendering experiments on subjects’
perception of the whiteness of illumination when in the presence of white
surroundings with or without colored objects.