December 2019
Volume 19, Issue 15
Open Access
OSA Fall Vision Meeting Abstract  |   December 2019
Illuminants estimated by human observers for natural objects under daylights compared with those predicted by the optimal color hypothesis
Author Affiliations
  • Kazuho Fukuda
    Kogakuin Univeristy
  • Takuma Morimoto
    University of Oxford
  • Ben Kusano
    Kanagawa University
  • Keiji Uchikawa
    Kanagawa Institute of Technology
Journal of Vision December 2019, Vol.19, 41. doi:
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      Kazuho Fukuda, Takuma Morimoto, Ben Kusano, Keiji Uchikawa; Illuminants estimated by human observers for natural objects under daylights compared with those predicted by the optimal color hypothesis. Journal of Vision 2019;19(15):41.

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      © ARVO (1962-2015); The Authors (2016-present)

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Color constancy is a visual function to perceive the world to be constant in color under various illuminants. The visual system must estimate an illuminant in a scene to achieve color constancy. It was reported that the optimal color hypothesis (Uchikawa et al., JOSA, 2012) computationally predicted physical illuminants better than other candidate models based on the mean chromaticity or on the mean cone signals, for the distribution of 400 colors in a color space calculated with the spectral surveys of natural objects and daylights (Uchikawa and Fukuda, ICVS 2017). In the present study, we carried out a psychophysical experiment to compare the predictions of the optimal color hypothesis and human illuminant estimations in the same color distributions. In the experiment, stimuli were presented on a CRT, consisting of 217 hexagonal elements: a center test and 216 surrounding elements. Each element subtended 1-deg in diagonal. The colors of the surrounding elements were calculated using spectral reflectances of 215 natural objects and spectral power distributions of five test daylights, which were both measured in natural environments in Japan. Five male observers with normal color vision participated in the experiment. Observers adjusted the chromaticity and luminance of the center test element so that it appeared as a full white paper (paper match) under a test daylight. The results showed that mean illuminant estimations obtained for each daylight condition are fairly close to the predictions of the optimal color hypothesis although individual differences in illuminant estimations were found large.

Uchikawa, Estimating illuminant color based on luminance balance of surfaces JOSA.A 292A133-A143 2012 [CrossRef]
Uchikawa, , Fukuda, Illuminant estimation by the optimal color hypothesis for natural objects and daylightsICVS 2017Germany2017
 This work was supported by JSPS KAKENHI Grant Number JP17H01809 and JP17K04503. TM's Ph.D studentship is funded by the Aso Scholarship, the Sasakawa Fund Scholarship, and awards from the Kikawada Foundation and the Japanese Student Services Organization.

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