PhD Research

From Color Science to Media & Entertainment Industry applications: by means of display, vision and quality models - beyond the limits of existing standards

Under this broad thesis title, my work focuses on observer variability and observer metamerism in the context of modern display colorimetry. Following is probably a good introduction of the topic:

One of the basic tenets of conventional applied colorimetry is that the whole population of color normal observers can be represented by a single “standard” observer with reasonable accuracy. The 1964 CIE 10° standard colorimetric observer has indeed served us well in all industrial color imaging applications, until recently. With the proliferation of modern wide-gamut displays with narrow-band primaries, color scientists and engineers face a new challenge. When colors are compared on two displays with very different spectral power distributions, color perception can vary significantly among color normal observers. Thus, using the CIE 10° standard observer in colorimetric computation in such applied context can lead to an unacceptable color match for many color normal observers. Conventional colorimetry has no means to predict this variation. 

In my thesis research, I am investigating this interesting technical challenge through theoretical analysis as well as visual experiments that prove the practical significance of this issue in the context of display applications.

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

Following publications have so far resulted from this work:

1. 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]
2. 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]
3. 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]
4. 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]
5. 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]

In the latest development, we have come up with a method for classifying various color normal observers into one of seven categories. The experimental setup is practical for industrial applications, even though we are working on further improving the tool and the method. This is something I am quite excited about, because this may one day lead to our dream application: observer-dependent color imaging, where the color workflow can be locally adjusted to achieve individualized color experience. More details to follow soon...

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

Bibliography

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.

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.