1. Principles of Color Technology
Chapter 4 Measuring Color Quality
-ROY S. BERNs
Speaker : Yi-Ling Chen (陳宜伶)
Advisor: Prof. Han-Ping D. Shieh (謝漢萍教授)
Prof. Yi-Pai Huang (黃乙白教授)
Institute of Electro-Optical Engineering,
National Chiao Tung University, Hsinchu, Taiwan
April

2. Outline Introduction Metamerism Indices Conclusions
- Color-difference research
Weighted Color-Difference Equations
- Prior Equation
- JPC 79 Equation
- CMC (l:c) equation
- BFD Equation
- CIE94
Color Tolerance Experiment
Metamerism Indices
Conclusions

3. Outline Introduction Metamerism Indices Conclusions
- Color-difference research
Weighted Color-Difference Equations
- Prior Equation
- JPC 79 Equation
- CMC (l:c) equation
- BFD Equation
- CIE94
Color Tolerance Experiment
Metamerism Indices
Conclusions

4. All current color digital-imaging standards and practices use CIELAB.
Introduction
Color-difference research
CIELUV CIELAB
CIELAB
Adams-Nickerson
McLaren
McDonald
Hunter
All current color digital-imaging standards
and practices use CIELAB.

5. Outline Introduction Metamerism Indices Conclusions
- Color-difference research
Weighted Color-Difference Equations
- Prior Equation
- JPC 79 Equation
- CMC (l:c) equation
- BFD Equation
- CIE94
Color Tolerance Experiment
Metamerism Indices
Conclusions

6. Weighted Color-Difference Equations (i) - Prior Equation
The earliest weighted equation
Nickerson
The optimized weighted equation
-1942 Adams-Nickerson
Developing a weighted equation requires
a dataset of visual judgments.

7. Weighted Color-Difference Equations (ii) - Example
RIT-DuPont dataset

8. JPC 79 Equation McDonald’s JPC 79 equation
The sensitivity of delta H is modified by chroma and hue angle in JPC 97 equation.

9. CMC Color-Difference Equation
Issues of McDonald’s JPC 79 equation
- Dark colors
- Near-neutral colors
McLaren CMC (l:c) equation
l ,c : weight of lightness and chroma
CMC (2:1) = McDonald’s JPC 79 equation
Compared with JPC 79 equation:
1. L*<16 SL=0.511 ,unless
The CMC equation is the optimized equation from JPC 79 equation by the user.

10. BFD Equation Dataset - Luo-Rigg dataset BFD Equation
The arithmetic mean values of standard and batch in C and h are used in BFD equation.

11. The reference condition is considered!
CIE94
Three dataset
-Writt
-Luo-Rigg
-RIT-DuPont
CIE 94 color difference equation
The reference condition is considered!

12. Outline Introduction Metamerism Indices Conclusions
- Color-difference research
Weighted Color-Difference Equations
- Prior Equation
- JPC 79 Equation
- CMC (l:c) equation
- BFD Equation
- CIE94
Color Tolerance Experiment
Metamerism Indices
Conclusions

13. Color Tolerance Experiment
Light source : illuminant F7
Sample size : 3 inches square
Observer : ˚ observer
Spectrophotometer : Largest aperture

14. It’s very difficult to have perfect correlation with visual estimates.
Results
Pass
Fail
80%
Optimized
CIE94
It’s very difficult to have perfect
correlation with visual estimates.

15. Outline Introduction Metamerism Indices Conclusions
- Color-difference research
Weighted Color-Difference Equations
- Prior Equation
- JPC 79 Equation
- CMC (l:c) equation
- BFD Equation
- CIE94
Color Tolerance Experiment
Metamerism Indices
Conclusions

16. The indices of metamerism are used.
The illuminant metamerism – Samples
The observer metamerism – Samples, Colored light
The mismatch occurs due to a change in illumination.
The mismatch occurs due to a change in observer.
The indices of metamerism are used.

17. Metamerism Indices The metamerism index
- metameric pair under a test condition
The weighted metameric index
Minimizing illuminant metamerism simultaneously minimizes observer metamerism.

18. Outline Introduction Metamerism Indices Conclusions
- Color-difference research
Weighted Color-Difference Equations
- Prior Equation
- JPC 79 Equation
- CMC (l:c) equation
- BFD Equation
- CIE94
Color Tolerance Experiment
Metamerism Indices
Conclusions

19. Conclusions
Either a uniform color-difference space or weighted color-difference equation can improve correlation.
A uniform color-difference space is always a better solution.
CIE forms a committee to establish more uniform color space for Industrial Color-Difference Evaluation.

20. Thank You for Your Kind Attention!20