Improved Methods for Computing CCT and D_uv

ABSTRACT

Recently, Ohno proposed a method for computing the correlated color temperature (CCT) of a light source and the shortest distance (with sign) between its chromaticity and that of the Planckian locus (D_uv). In Ohno’s method, firstly a lookup table is chosen, and then a hybrid method based on the triangular and parabolic solutions is used to predict the CCT and D_uv of a given light source. In this article, we found that spline interpolation is better than the parabolic solution for predicting CCT and D_uv. Therefore, we propose two new hybrid methods based on the triangular and either spline interpolation or third-order interpolation using two local function values and two local second-order derivative values. Comprehensive tests using the lookup table with both 1% and 0.25% increments relative to the current selected color temperature demonstrate that the proposed methods outperform Ohno’s method.

KEYWORDS:

• Chromaticity
• correlated color temperature
• D_uv
• light source
• spline interpolation

OCIS CODES

330.1690; 330.1710; 330.1730

OCIS CODES

330.1690; 330.1710; 330.1730

Acknowledgments

The authors thank Donald J. Murphy McVeigh for his help with English editing.

Disclosure statement

The authors have no financial interests to declare.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 61775169); Ministry of Science and Innovation of the Government of Spain (PID2019-107816GB-I00/SRA/10.13039/501100011033); The Natural Science Foundation of Liaoning Province, China (Grant No. 2020LNJC01); Department of Education of Liaoning Province, China (Grant No. LJKQZ2021127); and Graduate Education Reform and Science and Technology Innovation Entrepreneurship Project of the University of Science and Technology Liaoning (LKDYC202103).