CIELUV

CIELUV
Name	CIELUV
Other names	CIE 1976 L*u*v*
Developer	International Commission on Illumination
Introduced	1976
Based on	CIE 1931 color space
Type	Perceptually uniform color space
Primary use	Color difference evaluation, color specification

CIELUV CIELUV is a perceptually uniform color space developed by the International Commission on Illumination to improve on earlier models for chromaticity and color difference. It provides a device-independent framework for specifying colors and computing perceptual differences, widely used alongside CIELAB in industries ranging from Kodak and Xerox imaging to NASA remote sensing and Canon printing workflows. The model underpins standards adopted by organizations such as ISO and IEC for colorimetry and quality control.

Introduction

CIELUV was published by the International Commission on Illumination in 1976 to address nonuniformities in the CIE 1931 color space chromaticity diagram and to furnish a coordinate system tied to human visual perception for tasks used by companies like Mitsubishi Electric, Sony, Apple Inc., Microsoft, and research groups at MIT and Stanford University. The space expresses colors with three parameters L*, u*, v*, enabling quantitative comparisons used by General Electric and Siemens laboratories and influencing color standards at NIST and DIN. Its adoption extended into printing houses such as R.R. Donnelley and photographic firms like Fujifilm and Agfa.

Historical development and motivation

Development traces to the limitations observed in the CIE 1931 color space and critiques by researchers at institutions including Bell Labs, RCA Laboratories, Harvard University, University of Cambridge, and University of Tokyo. Motivations included improving uniformity for devices from Hewlett-Packard plotters to Panasonic displays and for industrial sectors—textile firms like Arkwright and automotive companies such as Ford Motor Company and Toyota Motor Corporation—seeking reliable color tolerancing. Influential contemporaries and alternate proposals came from groups at RCA, Eastman Kodak Company, and academics like researchers affiliated with University College London and the Royal College of Art, prompting standards bodies ISO and CEN to evaluate and endorse perceptually based metrics.

Color space definition and mathematics

CIELUV maps tristimulus values derived from CIE 1931 color space using white point references such as CIE Standard Illuminant D65 or CIE Standard Illuminant D50 and transformations used by industries including Pantone and X-Rite. Conversion begins with XYZ color space coordinates transformed by chromaticity functions of the CIE 1931 standard observer; mathematical operations incorporate nonlinear compression using functions developed in the same era as models from Munsell and research at Yale University. The L* axis corresponds to perceived lightness, while u* and v* denote chromaticity coordinates derived from ratios of X, Y, Z scaled by the chosen white point, methodologies echoed in standards promulgated by ISO 11664 and test methods at ASTM International. Matrix operations used in conversion are familiar to engineers at Intel, IBM, NVIDIA, and AMD, and the space integrates with color management systems deployed by Adobe Systems and W3C specifications.

Color difference metrics and applications

Color differences in CIELUV are commonly computed using Euclidean distances ΔE*uv, applied in quality control by firms such as Procter & Gamble, Unilever, and Nestlé for packaging color consistency, and by paint makers like Sherwin-Williams and AkzoNobel to set tolerances. For improved perceptual uniformity, researchers have proposed corrections and metrics (e.g., CIE94, CIEDE2000) developed with contributions from laboratories at University of Leeds, University of Manchester, and Rensselaer Polytechnic Institute; these metrics influenced standards at ISO and testing protocols in Automotive Industry Action Group. Applications include textile color matching at Nike, display calibration at Samsung Electronics and LG Electronics, and color grading in film post-production companies like Industrial Light & Magic and Pixar.

Practical uses and limitations

Industries implementing CIELUV include digital imaging firms such as Kodak, Canon, Nikon Corporation, and Olympus Corporation; paint and coating manufacturers like Benjamin Moore; and color measurement instrument makers including Konica Minolta and X-Rite. Limitations arise for highly saturated colors near spectral locus points studied by spectroscopists at CSIRO and Scripps Institution of Oceanography, where perceptual nonuniformities persist and alternative models or gamut mapping strategies by companies like HP Inc. are preferred. CIELUV assumes a particular observer angle and illuminant, invoking standards from CIE and calibration practices used at RAL and validation labs at UL Solutions.

Implementation and conversion algorithms

Implementations convert between device color spaces (e.g., sRGB, Adobe RGB (1998), Rec. 709) and CIELUV via intermediate XYZ color space with chromatic adaptation transforms like Bradford transform or Von Kries transform, algorithms incorporated into color management modules by LittleCMS, ArgyllCMS, and software suites from Adobe Systems and OpenColorIO. Practical conversion code appears in libraries used by Google, Mozilla, and Apple Inc. with optimizations for GPUs from NVIDIA and AMD. Test imagery and datasets for verification originate from institutions such as Getty Research Institute and benchmarking bodies like SMPTE and ITU-R. For high-precision workflows, manufacturers such as Xerox and Ricoh integrate spectral data and use multispectral imaging methods developed at University of Arizona and ETH Zurich.

Category:Color space