Color Science Ph.D Defense: Color Change: Illumination and Observers

Integrated Science Academy
Color Change: Illumination and Observers

Che Shen
Color Science Ph.D. candidate

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Abstract:
While color change is often associated with physical or chemical alterations in an object, this thesis focuses on perceptual color changes due to factors like color inconstancy under different lighting conditions, observer metamerism due to varying color matching functions, and individual differences in hue perception despite identical tristimulus values.
Based on the complexities of color change phenomenon, a psychophysical experiment was conducted to establish the threshold of color inconstancy, where observers were tasked with categorizing colors under varying lighting. A major advancement in this thesis is the development of the Weighted Geometric Mean (WGM) model, an advanced chromatic adaptation model grounded in the principle that sensory adaptation follows a geometric mean approach. This model marks a significant progression in understanding and predicting color adaptation under various lighting conditions.
A key finding from the psychophysical experiments is the impracticality of using unique hues as a reference for assessing observer metamerism. This insight led to the development of the innovative observer metamerism index, which utilizes individual color matching functions (CMFs) and a simulation approach to quantify metamerism more effectively. Additionally, a cross-media color-matching experiment, merging physical pigments with self-emitted light display, is presented to assess individual color matching functions. This experiment challenges existing standards and demonstrates the effectiveness of personalized CMFs in color reproduction, enhancing the accuracy of color perception.  
Another significant contribution of this thesis is the development of an algorithm for hue appearance equalization, tailored to the unique hue perception of individual observers. The effectiveness of this algorithm is validated through a user study indicating the influence of memory color and highlight the need for further exploration into the real-world application of hue adjustment techniques.

Intended Audience:
All are welcome.

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