How Modern Displays Push Conventional Colorimetry to Its Limit Abhijit Sarkar* , **, Laurent Blondé*, Patrick Le Callet**, Florent Autrusseau**, Patrick Morvan*, Jürgen Stauder* CREATE 2010, Gjøvik, Norway June 8, 2010 *Technicolor Research & Innovation , France **IRRCCyN-IVC, University of Nantes, France 1
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How Modern Displays Push Conventional Colorimetry to Its Limit Abhijit Sarkar*, **, Laurent Blondé*, Patrick Le Callet**, Florent Autrusseau**, Patrick.
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How Modern Displays Push Conventional Colorimetry to Its Limit
Abhijit Sarkar*,**, Laurent Blondé*, Patrick Le Callet**,
Florent Autrusseau**, Patrick Morvan*, Jürgen Stauder*
CREATE 2010, Gjøvik, Norway
June 8, 2010
*Technicolor Research & Innovation , France
**IRRCCyN-IVC, University of Nantes, France
1
About Me…
2
B.E. Electrical Engineering, Jadavpur University,
India, ‘00
M.S. Architectural Engineering (Lighting), Penn
State University, Pennsylvania, ‘05
MS Color Science, Munsell Color Science Lab,
RIT, Rochester, ’08
Currently: PhD Student at
• Technicolor Research & Innovation, Rennes, France
(Advisors: Laurent Blondé, Jürgen Stauder)
• University of Nantes , France (Advisors: Patrick Le
Callet & Florent Autrusseau)
Current Research Topic:
Observer variability issue in modern display
colorimetry
What is Color? How Do We Measure It?
Color is a perception that depends on the response of the human
visual system to light, and the interaction of light with objects
(also called color stimulus)
3
0.15470.70290.1424
Spectral Power Distribution
Spectral Sensitivity of
Photoreceptors
Tristimulus Values
Quantitative Representation of Color
ySk
zRSkZ
yRSkY
xRSkX
100
: Spectral power distribution of a CIE illuminant (e.g. D65) S
R
zyx ,,
: Spectral reflectance factor of the object
: CIE standard observer 2° or 10° color-
matching functions
ZYX
Xx
Common representation: xyY
4
Similar for y and z
In colorimetry, there is a provision for changing the illuminant and the object, but not the observer!
5
Average Observer
Observer Metamerism: The color is in your eyes!
Two color stimuli with very different spectral power
distributions can be a match for one observer and mismatch
for the other
6
The more different the spectral power distributions are, the more prominent the effect of metamerism is!
7
Observer Metamerism on a CRT and an LCD: Simulation
XYZ (10° SO and
D65)
dcCRT/LCD(10°)
XYZCRT/LCD(obs1)
M-1CRT/LCD (10°)
XYZCRT/LCD(obs2)
dcCRT/LCD_obs1
(CRT equiv.)
dcCRT/LCD_obs2
(CRT equiv.)
MCRT/LCD (obs2)MCRT/LCD (obs1)
M-1CRT (obs1) M-1
CRT (obs2)
CRT LCD
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Obs. 1 (cat. 5)
Obs. 2 (cat. 6)
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CRT LCD
Obs. 1 (cat. 5)
Obs. 2 (cat. 6)
A Color Matching Experiment Using Two Displays
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Displays: a narrow-band LCD with LED backlight and a
broad-band studio CRT
Observers asked to adjust the color on the left half of
the bipartite field (matching field) to match the color on
the right half (test field)
text
LCD
CRT
10° Mask
Mirror
10°
Projector
Mask
Preliminary Results from the Color Matching Experiment
Standard observer-predicted color differences (∆E*00) of
individual observer color matches found to be significant
for some observers 11
Conclusions
12
In highly color-critical applications using modern displays,
employing an average observer model in colorimetry can
possibly lead to unacceptable color matches for many
color-normal expert observers
Objective of this work:
To develop an observer-dependent color imaging method,
where color workflow in a display device can potentially be
tuned to one of several observer classes, leading to novel
industrial applications
Thank you!
13
Acknowledgments
Jean-Jacques Sacré for his help and guidance in preparing the
experimental setup
Following colleagues for being the observers in the color matching
experiments:
• Laurent Blondé• Patrick Morvan• Jürgen Stauder• Arno Schubert• Pascal Bourdon• Séverine Baudry• Emmanuel Jolly• Catherine Serre• Jean-Jacques Sacré
Hypotheses: Solution Lies in the Problem Itself…
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Color vision of observers can be classified into a small
number of categories
A practical experimental setup can be built to classify
observers
Color processing in an industrial application can be tuned
to one of these categories, leading to a better agreement
between real observer perceptions and colorimetry
Work-in-Progress: A Novel Experimental Method for Observer Classification
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Seven Observer Categories (sets of CMFs) + CIE 10° observer
Rate categories for many colors:unacceptable, acceptable and
satisfactory
Determine observer category
Observer Categories Through Statistical Analysis of Color-Matching Dataset
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4 x- functions 3 y-
functions
3 z- functions
Results: Observer Classification
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For eleven observers, the CIE 10° standard observer (category
1) was not among the two most preferred categories
For three observers, category 1 was rejected as an
unacceptable match for all fifteen test colors
Conclusions
18
In highly color-critical applications using modern displays,
employing an average observer model in colorimetry can
possibly lead to unacceptable color matches for many color-
normal expert observers
Real, color-normal observers can be classified into a small
number of categories by means of a practical experimental
setup suitable for industrial applications
Objective of this work:
To develop an observer-dependent color imaging method, where
color workflow in a display device can potentially be tuned to one
of several observer classes, leading to novel industrial applications
Thank you!
19
Acknowledgments
Jean-Jacques Sacré for his help and guidance in preparing the
experimental setup
Following colleagues for being the observers in the color matching
experiments:
• Laurent Blondé• Patrick Morvan• Jürgen Stauder• Arno Schubert• Pascal Bourdon• Séverine Baudry• Emmanuel Jolly• Catherine Serre• Jean-Jacques Sacré