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Two families of colour rendering judgements
F. Viénot, E. Mahler, A. Rambaud, M.-L. Durand, S. Bailacq,
C. Boust, J.-J. Ezrati,CRCC, Muséum national d’histoire naturelle
CIE, TC1-69, Budapest, June 2009
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Two families of colour rendering judgements
• Fidelity– Discrimination– Preserved metamerism– Naturalness– Chromatic consistency– Transparent clarity– Skin tone– Comfort, relaxation– Harmony?
• Colourfulness enhancement– Appearance– Brightness– Attractiveness– Beautification– Chromatic clarity– Selective chromatic contrast– Conspicuity?
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Colour rendering - Discrimination
• Distribution of errors
Errors of neighbourhood of each cap
0
1
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1 4 7 10 13 16 19 22 25 28 31
32 caps
Nu
mb
er
of
err
ors
of
ne
igh
bo
urh
oo
d
Solux WWARGB WR RGBA RGB
RGB
Solux
Mahler E., Ezrati J.-J., Viénot F., 2009, Testing LED Lighting for Colour Discrimination and Colour Rendering. Color Research & Application, 34 : 8-17.
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Colour rendering - Appearance
• Distribution of colourfulness ratings
Col
ourf
ulne
ss r
atin
g
Visual appearance experiment
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R Y50R Y G50Y G B50G B R50B R
NCS sample code
Obs
erv
ers
ratin
g
Solux
RGB
RGBA
WR
WWARGB
RGB
Colourfulness ?Colourfulness ?
F. Viénot , J.-J. Ezrati, C. Boust, E. Mahler, “Grading LED illumination: from colour rendering indices to specific light quality indices”, CIE 26th session D1, pp. 22-25, (2007)
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CIELAB colour specification
A paradox
• Colour discrimination impairment
AND
Colorfulness enhancement
C32 caps under real illuminations
-30
-20
-10
0
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-30 -20 -10 0 10 20 30
a*
b*
Solux WWARGB WR RGBA RGB
RGB
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Two families of colour rendering judgements
• Other works– Szabó F, Schanda J, Bodrogi P, Radkov E. A Comparative
Study of New Solid State Light Sources. Proc. CIE 26th Session, 2007, D1:18-21.
– Y. Nakano, H. Tahara, K. Suehara, J. Kohda, T. Yano, “Application of multispectral camera to colour rendering simulator”, AIC Colour 05, pp. 1625-1628, (2005)
– Rea Mark S., Freyssinier-Nova Jean P., 2008, Color Rendering: A Tale of Two Metrics, COLOR research and application, 33: 192-202.
– Van Kemenade J.T.C., P. J. M. Van Der Burgt , "Towards a user oriented description of colour rendition of light sources". CIE 119 - 1995 - 23rd Session, New Delhi, pp. 43-46, 1995. See also CIE, Beijing, 2007
– S. Jost-Boissard, in this conference– Fotios, in this conference ?
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A vector field
Van Kemenade J.T.C., P. J. M. Van Der Burgt , "Towards a user oriented description of colour rendition of light sources". CIE 119 - 1995 - 23rd Session, New Delhi, pp. 43-46, 1995.
VIÉNOT F., BENHALIMA F., BRETTEL H., BOURDONCLE B., COLONNA DE LEGA A., 2002, Rating of tinted ophthalmic lenses, in 9th Congress of the International Colour Association, Proceedings of SPIE Vol. 4421, 271-274.
We proposed two statistical indices: “norm” and “disorder”
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Two families of colour rendering judgements
• Fidelity and colourfulness cannot be achieved simultaneously.
• Different tasks and objectives, different visual mechanisms.
• We need different indices, – sort CQS ideas – revise CRI, see TC 1-33 update – create new indices
• Incices should give precise information (field vectors)
J. Schanda, Color rendering of light sources, In: János Schanda (Editor) Colorimetry, Understanding the CIE system, Wiley, pp. 207-217. W. Davis, Y. Ohno, “Toward an improved color rendering metric”, Proc. Solid State Lighting V, SPIE Vol. 5941, pp.283-290, (2005)
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Issued May 2009
The book begins with the principles of LED lighting, then focuses on issues and challenges. Chapters are devoted to key steps in LED manufacturing: substrate, epitaxy, process and packaging. Photoelectric characterization of LEDs, Lighting with LEDs and the imposition of a certain level of color quality, are the subject of later chapters, and finally there is a detailed discussion of the emergence of OLEDs, or organic LEDs, which have specific capabilities of immediate interest and importance in this field.
