My Research

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PhD Research

Identification and Assignment of Colorimetric Observer Categories and Their Applications in Color and Vision Sciences

My PhD thesis focused on the effect of observer color perception variability (also called observer metamerism) in modern displays with narrow-band primaries. Through experiments and theoretical analyses, this work showed that (color normal) observers perceive colors quite differently, and this can be a major issue in color-critical professional applications involving modern wide-gamut displays. In particular, this variability becomes apparent when colors are compared on two systems with very different spectral power distributions

In addressing this issue, we envisaged a new color processing framework called Observer-dependent Color Imaging, which would help us achieve personalized color processing. This addresses a fundamental limitation of colorimetry, which assumes a single observer model can reasonably represent the whole population of color normal observers. As part of this thesis research,  a method was  developed to classify observers as belonging to one of the seven representative observer categories (or models) derived through statistical analysis. 

A low-cost, portable, early proof-of-concept prototype called "Observer Calibrator" was developed for classifying color normal observers based on their color vision. The prototype is equipped with two trichromatic LED light sources with very different spectral characteristics (highly metameric). In each trial, different versions of color matches are shown in a bipartite field, where each version corresponds to an observer category (or model). For a given observer, the version consistently producing superior matches over several trials gives his/her category. Such a device or method can not only address observer metamerism, but can also prove extremely useful in general color research that involves visual experiments. Collaborative experiments were performed in February 2011 with two laboratories in Europe involved in color research.

At Technicolor Research & Innovation, I received guidance from Dr. Laurent Blondé and Dr. Jürgen Stauder, (Principal Scientists), and a major developmental support from Mr. Patrick Morvan (Researcher). At the university, my advisor was Prof. Patrick Le Callet and co-advisor was Dr. Florent Autrusseau.

Full thesis is available here (6.6 MB).

Eight observer categories (i.e. color-matching functions) derived as part of this work are available here as an excel spreadsheet.

Following publications have so far resulted from this work:

  1. A. Sarkar, L. Blondé, “Colorimetric Observer Categories and Their Applications in Color and Vision Sciences", CIE Centenary Conference, April 2013 [PDF]
  2. A. Sarkar, F. Autrusseau, F. Viénot, P. Le Callet, L. Blondé, “From CIE 2006 Physiological Model to Improved Age-Dependent and Average Colorimetric Observers”, Journal of the Optical Society of America (JOSA A), 28(10): pp. 2033-48, 2011 [PDF]
  3. M. Fetudina, A. Sarkar, P. Urban, P. Morvan, “(How) Do Observer Categories Based on Color Matching Functions Affect the Perception of Small Color Differences?”, in Proceedings of the 19th Color and Imaging Conference, San Jose, CA, 2011 [PDF]
  4. P. Morvan, A. Sarkar, J. Stauder, L. Blondé, J. Kervec, S.K. Hasan, “A handy calibrator for color vision of a human observer”, IEEE International Conference on Multimedia and Expo (ICME), Barcelona, 2011 [PDF]
  5. A. Sarkar, L. Blondé, P. Le Callet, F. Autrusseau, J. Stauder, P. Morvan, “Toward Reducing Observer Metamerism in Industrial Applications: Colorimetric Observer Categories and Observer Classification”, in Proceedings of the CIC18 conference, San Antonio, Texas, 2010 [PDF]
  6. A. Sarkar, L. Blondé, P. Le Callet, F. Autrusseau, J. Stauder, P. Morvan, “Modern displays: why we see different colors, and what it means?”, 2nd European Workshop on Visual Information Processing (EUVIP/IEEE), Paris, 2010 [PDF]
  7. A. Sarkar, L. Blondé, P. Le Callet, F. Autrusseau, J. Stauder, P. Morvan, “How Modern Displays Push Conventional Colorimetry to its Limit”, Colour in art, science, design, conservation, research, printmaking, digital technologies, textiles (CREATE), Gjøvik, Norway, 2010 [PDF]
  8. A. Sarkar, L. Blondé, P. Le Callet, F. Autrusseau, J. Stauder, P. Morvan, “A color matching experiment using two displays: design considerations and pilot test results”, in Proceedings of the CGIV 2010 conference, Joensuu, Finland, 2010 [PDF]
  9. A. Sarkar, L. Blondé, P. Le Callet, F. Autrusseau, J. Stauder, P. Morvan, “Study of Observer Variability on Modern Display Colorimetry: An Analysis of CIE 2006 Model”, in Proceedings of the11th Congress of the International Colour Association (AIC) 2009, Sydney, Australia, 2009 [PDF]
  10. A. Sarkar, L. Blondé, P. Le Callet, F. Autrusseau, J. Stauder, P. Morvan, “Study of Observer Variability on Modern Display Colorimetry: Comparison of CIE 2006 Model and 10° Standard Observer”, in Proceedings of the 11th Congress of the International Colour Association (AIC) 2009,Sydney, Australia, 2009  [PDF]

This PhD thesis resulted in two patent applications:

  • A. Sarkar, L. Blondé, P. Morvan, “Method for the classification of observers according to their visual characteristics”, European Patent Application #10290193.1, filed by Thomson Licensing on April 9, 2010
  • A. Sarkar, L. Blondé, J. Stauder,  “Method for controlling an image display device to allow the same perception of colours over a large variety of observers”, European Patent Application #10290194.9, filed by Thomson Licensing on April 9, 2010

MS Color Science Thesis Research

Evaluation of the Color Image and Video Processing Chain and Visual Quality Management for Consumer Systems

The research was sponsored by Intel Corp. My advisor was Prof. Mark Fairchild.

Abstract: With the advent of novel digital display technologies, color processing is increasingly becoming a key aspect in consumer video applications. Today’s state-of-the-art displays require sophisticated color and image reproduction techniques in order to achieve larger screen size, higher luminance and higher resolution than ever before. However, from color science perspective, there are clearly opportunities for improvement in the color reproduction capabilities of various emerging and conventional display technologies. This research seeks to identify potential areas for improvement in color processing in a video processing chain. As part of this research, various processes involved in a typical video processing chain in consumer video applications were reviewed. Several published color and contrast enhancement algorithms were evaluated, and a novel algorithm was developed to enhance color and contrast in images and videos in an effective and coordinated manner. Further, a psychophysical technique was developed and implemented for performing visual evaluation of color image and consumer video quality. Based on the performance analysis and visual experiments involving various algorithms, guidelines were proposed for the development of an effective color and contrast enhancement method for images and video applications. It is hoped that the knowledge gained from this research will help build a better understanding of color processing and color quality management methods in consumer video.

Full thesis is available here (compressed PDF: 41 MB). Individual chapters are available below, also in PDF format:

Chapter 0: Abstract, Acknowledgment, Table of Contents etc

Chapter 1: Introduction

Chapter 2: Color Video Processing

Chapter 3: Video Quality Assessment

Chapter 4: Methods for Color and Contrast Enhancement in Images and Video

Chapter 5: Implementation and Performance Analysis of Several Color/Contrast Enhancement Algorithms (15 MB)

Chapter 6: Psychophysical Evaluation of Three Algorithms (Compressed PDF: 31 MB)

Chapter 7: Conclusions


Appendix A: Algorithm Performance Analysis Plots (Compressed PDF: 20 MB)

A paper was published in Color Imaging Conference in November 2008. A draft of the paper is available here.

This MS thesis resulted in a patent application:

A. Sarkar, J.E. Caviedes, and M. Subedar, “Joint enhancement of lightness, color and contrast of images and video”, US Patent Application #20100085487 filed by Intel Corporation on September 30, 2008


Independent Research: Lighting

A Proof-Of-Concept Application of Digital Imaging in Lighting Control - Integrating Daylight and Occupancy Sensing

In February 2007, I completed this independent research project on a new and interesting application of a high dynamic range CMOS image sensor originally developed for automotive video applications. The project was funded by my department, the Center for Imaging Science (CIS) under the CIS-Kodak Grant for Innovative Graduate Student Research Proposals. Prof. Mark Fairchild and Prof. Carl Salvaggio were my advisors. This was a continuation of my MS thesis research at Penn State. Here is a draft of the paper published in Electronic Imaging 2008, San Jose, CA.

MS Lighting Thesis Research

It was a proof-of-concept research for a novel application of High Dynamic Range imaging technique in automated lighting control. My advisor was Prof. Richard Mistrick. The thesis is available here

A draft of a paper published in the April 2006 issue of IESNA journal (LEUCOS) is available here.

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This page was last modified on July 15, 2013. Modified 10 times since 28th July 2008.

Copyright© Abhijit Sarkar 2011. All rights reserved.